THE CHALLENGES OF WEARABLE COMPUTING: PART 1

WEARABLE COMPUTING PURSUES AN INTERFACE IDEAL OF A CONTINUOUSLY

WORN, INTELLIGENT ASSISTANT THAT AUGMENTS MEMORY, INTELLECT,

CREATIVITY, COMMUNICATION, AND PHYSICAL SENSES AND ABILITIES.

MANY CHALLENGES AWAIT WEARABLE DESIGNERS AS THEY BALANCE

INNOVATIVE INTERFACES, POWER REQUIREMENTS, NETWORK RESOURCES,

AND PRIVACY CONCERNS. THIS SURVEY DESCRIBES THE POSSIBILITIES

OFFERED BY WEARABLE AND, IN DOING SO, DEMONSTRATES

ATTRIBUTES UNIQUE TO THIS CLASS OF COMPUTING.

Wearable computing can describe a portability during operation; enable hands- broad range of devices and concepts. At the free or hands-limited use; can attract the user’s time of this writing, wearables are generally attention, even when not in active use; can equated with head-up, wearable displays; one- run continuously; and attempt to sense the handed keyboards; and custom user’s current context.1 Kortuem et al. employ worn in satchels or belt packs. Figures 1 similar criteria but use the term augmented through 4 show members of the Massachu- reality to describe “the technique setts Institute of Technology’s Wearable Com- that allows focusing the user’s attention and puting Project with some of their wearable presenting information in an unobtrusive, devices. Unfortunately, the public often char- context-dependent manner.”2 Meanwhile, acterizes the field by its gadgetry instead of its Mann describes wearables as constant and goals. Ideally, wearable computing can be always ready, unrestrictive, not monopolizing Georgia Institute of described as the pursuit of a style of interface of user attention, observable and controllable as opposed to a manifestation in hardware. by the user, attentive to the environment, use- Technology This article develops goals and challenges for ful as a communication tool, and personal.3 wearable computing, and promotes discus- This article defines wearable computing sion in design techniques by suggesting meth- through the effort to achieve a hypothetical, ods, albeit sometimes fanciful, of addressing ideal wearable . Much of this phi- these challenges. losophy reflects the concept of a cyborg or a man-computer symbiosis as introduced in What is wearable computing? 1960. Manfred Clynes and Nathan Kline Several authors have defined wearable com- originally coined the term cyborg to describe puters by desirable characteristics. For exam- a human and machine combination where the ple, Rhodes states that wearables provide interface becomes a natural extension of the

44 0272-1732/01/$10.00  2001 IEEE Figure 2: Private Eye head-up display and simulated view. The wearer’s visual Figure 1. Wearable computing platforms “shares” images from both eyes to create worn by members of the Massachusetts the illusion that the wearer sees through the Institute of Technology’s Wearable Comput- opaque display. ing Project. Photo by Sam Ogden

Figure 4: Functional chording keyboard embroidered into a jacket. Photo courtesy of Rehmi Post and Maggie Orth Figure 3: MicroOptical’s display embedded in a pair of eye- glasses. The actual display is in the earpiece. An optical path deflects the image through the lens to a half-silvered mirror that reflects the image to the user’s eye. Photo by Sam Ogden

user. This interface would not require much …a subclass of man-machine systems. conscious attention, such as when a person There are many man-machine systems. At rides a bicycle. Although Clynes and Kline’s present however, there are no man-com- aim was adapting humans for the rigors of puter symbioses…. The hope is that, in space travel, the same concept might be not too many years, human brains and applied to systems that assist the user on other computing machines will be coupled physical and intellectual levels. J.C.R. Lick- together very tightly and that the resulting lider expresses this in Man-Computer Symbio- partnership will think as no human brain sis where he defines the title term as has ever thought and process data in a way

JULY–AUGUST 2001 45 WEARABLE COMPUTING

not approached by the information- adapt to its user over time, and encourage per- handling machines we know today. sonalization of its interface.

Ideal attributes Augment and mediate interactions with the To achieve the tight partnership suggested by user’s environment. The wearable should pro- Licklider, the computer must be a user’s con- vide universal information support in both stant companion. It must share the experiences the physical and virtual realms. For example, of the user’s life, drawing input from the user’s the wearable should automatically gather environment to learn how the user reasons and information and resources relevant to a par- communicates in relation to the world. As it ticular physical location and filter this infor- learns, the computer can provide increasingly mation based on the user’s current needs and useful and graceful assistance. Ideally, a wear- preferences. The wearable should mediate able should have several key attributes. between automation or computation in the environment and the user to present an inter- Persist and provide constant access to information face consistent with the user’s preferences and services. Designed for everyday and continu- abilities. In addition, the wearable should ous use, the wearable can interact with the manage potential interruptions, such as phone user at any given time, interrupting when nec- calls or e-mail, to best serve its user. essary and appropriate. Correspondingly, the Obviously, these attributes are ambitious, user can access the wearable quickly and with requiring a very detailed user model of the little effort. Such a device must be mobile and wearer. However, in striving to achieve this physically unobtrusive. goal, research efforts could reveal new insights about intelligence and human-computer Sense and model context. To provide the best interfaces. cognitive support for the user, the wearable must observe and model the user’s environ- Why use wearable computers? ment, the user’s physical and mental state, and Some people wear too many computers. A its own internal state. In some cases, the user businessman in Hong Kong might carry a per- could provide explicit contextual cues to help sonal digital assistant (PDA), a cellular tele- the wearable in its task. To provide parity, the phone, a pager, a computer, an wearable should inform the user of its own electronic translator, and a wrist- status, either through an explicit display or . These devices all contain very similar through subtle background cues. In addition, components: a microprocessor, memory, a the wearable should make its models observ- screen, a keyboard or input stylus, a battery, able so that the user can identify misunder- and, in some cases, a modem. standings and explicitly tutor the wearable As technology evolves, portable consumer when necessary. devices are beginning to have similar compo- nents as well. For example, computer-driven Adapt interaction modalities based on the user’s MP3 players replace CD players, solid-state context. The wearable should adapt its input audio digitizers replace portable Dictaphones, and output modalities automatically to those digital cameras are beginning to supplant film- that are most appropriate and socially grace- based cameras, and digital camcorders have ful at the time. For example, while attending outmoded their analog counterparts. The a meeting, the wearable could communicate main distinctions between these devices are with its user through a head-up display. How- the interface and the application software. ever, when the user enters his or her car to Wearable computers could exploit the com- drive home, the wearable could switch to an monality in components to eliminate cost, audio-only interface. In many instances, the weight, and redundancy and to improve con- computer interface will be secondary to the nectivity and services. user’s primary task and should demand the For example, imagine a box the size of a minimal necessary amount of the user’s atten- deck of cards that encloses a powerful yet ener- tion. In addition, the interface should guar- gy-conserving CPU and a large-capacity data antee privacy of interaction when appropriate, storage device. This pocket-sized wearable

46 IEEE MICRO computer has one output display—an LED to indicate that it is on and that its wireless network is functioning. This wireless network Wireless connects to the wearable computer video in a radius of about two to three meters cen- tered at the body. PC By choosing peripherals, the user defines Gesture this wearable computer’s functionality. For Pendant example, wireless earphones allow access to Control devices MP3 files stored on the wearable computer’s Slink-e X10 hard drive. Adding a walnut-sized camera and the appropriate software transforms the wear- able into a camcorder. With an Internet modem, the wearable becomes a pager, cellu- Control signals to devices lar phone, Web browser, and e-mail reader. Connecting medical sensors to the wearable Television Stereo system Lava lamp concentrates many diagnostic and recording devices into one unit. Figure 5. Using a near-infrared computer Thus, wearable computing and a wireless vision and lighting system, the Gesture Pen- body-centered network reduce component dant lets users control appliances through redundancy. In addition, functionality gestures. The Slink-e converts control instruc- increases as derivative services arise, leverag- tions from a computer’s serial port and the ing the convergence of media on the body. X10 is a home automation control standard The portable-consumer-electronics market that communicates with signals over electri- will become fertile ground for rapid innova- cal lines. tion. Companies can quickly respond to a new need or niche market with an appropriate or software without redesigning ple, depending on which object the wearer subsystems for each iteration. Sophisticated faces, raising or lowering a finger in front of portable electronics will become cheaper and the pendant might raise or lower the volume more powerful for the consumer, and the of a stereo, increase or decrease the temper- computer industry will have a new, attractive ature setting on a thermostat, and brighten upgrade path to pursue. or dim light settings on a lamp. Thus, the user could define or learn one interface and Mediate interactions then apply it repeatedly to many different The introduction of the windows, icon, devices, depending on context. menu, and pointer desktop metaphor in Imagine a more general-purpose wearable GUIs provided a means for user interfaces computer that, through software, adapts to to mediate between applications and the provide a consistent interface to any elec- user. Similarly, wearable computers will help tronics or computer systems in the environ- provide a consistent interface to computa- ment. For example, in a hotel, the wearable tionally augmented objects in the physical might provide access to the room’s alarm world. For example, the Gesture Pendant, clock and television through an interface con- shown in Figure 5, acts as a universal remote sistent with the user’s home system. The control that replaces button pushing with infrastructure needed for such interface simple . The Gesture adaptability will be a boon to the handi- Pendant is worn as a broach or necklace and capped. An individual can carry an interface detects hand movements performed in front appropriate for his abilities that automatical- of the body. The device recognizes these ges- ly adapts to the services provided by the elec- tures to provide control over electronics. tronics in the environment. For example, for Since many functions are similar across a blind user of an automated teller machine, devices, one gesture could provide an intu- the wearable can provide an audio version of itive command for many devices. For exam- the interface.

JULY–AUGUST 2001 47 WEARABLE COMPUTING

Aid communication rich virtual realities onto the physical world. The wearable can also assist in human-to- Wearable computers make mobile augment- human communication. Imagine that an Eng- ed reality practical. In a sense, augmented real- lish-speaking traveler from the US visits ity is a combination of the application Mexico. He could use a general-purpose wear- domains described previously: mediating able to scan menus and signs and translate between the user and environment, assisting them into English. Similarly, when convers- human-to-human communication, and pro- ing, the wearer can use a head-up display, as viding context sensitive reminders. shown in Figure 3 and a one-handed keyboard Instead of restricting the Web to desktop to quickly search an online phrase book for computer monitors, wearable computers will appropriate English phrases, which the user or let any object or location in the physical world even the wearable then says in Spanish. Going serve as a hypertext link.5 Museum visitors and further, the wearable could employ speech tourists will discover information about arti- recognition and directly translate English into facts simply by staring at them, triggering Spanish. Such systems are no longer purely associated hypertext presentations. By allow- speculative. Carnegie Mellon researchers have ing annotation, augmented-reality objects will already demonstrated an English-to-Croatian let friends and colleagues leave private mes- wearable speech translator for use in the Bosn- sages for each other at offices, restaurants, or ian peacekeeping mission.4 street corners. Wearable computers can also help manage The creation of an infra- interruptions in the user’s daily life. With the structure will lead to unexpected derivative spread of cellular phones, more people are aware uses. A powerful scenario involves advertis- of the inconvenience of an untimely interrup- ing, sales, and distribution. tion. Through sensors such as , microphones, and caller identification devices, As a wearer walks down a New York City wearable computers can determine the user’s avenue, a billboard advertising jeans begins current context and adapt appropriately. For transmitting information to the user’s example, if the user is in a noisy environment, wearable computer. Because the user is an audible ring might be appropriate. Howev- occupied looking at his calendar, the wear- er, interrupting the user during a business meet- able computer conveys to the billboard ing is inappropriate, unless the identity of the that all but the most interesting advertising caller is the user’s spouse and the situation is an overlays are turned off, and the billboard emergency. In such instances, the wearable begins a negotiation process for the user’s might switch to an instant messaging service attention. After asking the wearable the displayed in the wearer’s eyeglasses so that the user’s trousers size, a piece of information wearer can assess the situation and excuse her- the user has given his prior approval to self gracefully, if needed. make public, the billboard hooks into the supplier’s local inventory and discovers that Provide context-sensitive reminders they have an overstock in that size. The Context-sensitive interfaces will become billboard offers its product at a discount. very powerful with wearable computers. The new price causes the wearable com- Instead of simply acting as a virtual secretary, puter to whisper the offer discretely in the the wearable could be proactive and intimate, user’s ear. The user, now interested, turns listening to the wearer’s conversations and to see an animated advertisement tailored providing reminders as appropriate. Such to his interests overlaid on the billboard. reminders might be the text of the last e-mail Deciding that the product is worth the message exchanged between the conversation’s price, the user commits to the purchase participants, the definition of an unknown and the wearable computer transfers word, or recommendations on local restau- money and exchanges address information rants that both participants would enjoy. with the billboard. The billboard reroutes an express delivery truck to drop off the Augment reality jeans at the wearer’s house within the next Augmented reality overlays information- two hours.6

48 IEEE MICRO Obviously, this form of just-in-time infor- designs where peripherals are connected wire- mation delivery can provide powerful tools lessly to a central , supplying for the retail, advertising, and delivery indus- power becomes even more complicated. Each tries. In general, wearable computers could peripheral requires its own power source, lead to unanticipated hardware, software, and which may fail independently of the other service industries, possibly triggering changes components, possibly resulting in unreliabil- similar in scope to those of making the Inter- ity or high maintenance costs. net publicly available. However, many tech- Wearable computing presents particular nical, social, and logistical challenges lie ahead variations of this problem. Ultimately, wear- in creating appropriate devices for consumer able computers are clothes. A user might wear markets. a display in a pair of sunglasses, keep a com- puter in a belt buckle, and have a keyboard Challenges woven into a jacket.7 When the wearable com- To provide wearable computing, designers puter’s functionality is spread among subsys- must overcome significant challenges. As with tems distributed over the body, power any computing system, good software and distribution becomes complicated. If the com- hardware engineering methodologies enable ponents’ battery lives are too short, the user stable advancement. Indeed, wearable com- will soon get frustrated with the effort need- puting has inherited many of the systems ed to keep the system powered. One solution issues with which the general computing com- is to create long-lasting power supplies. For munity grapples. However, wearables repre- example, plutonium-238 power sources, such sent a current extreme in computing because as those implanted with pacemakers in the late researchers have not thoroughly studied the 1980s, can last for decades (see the “Pace- area’s design trade-offs. To encourage discus- makers and Power” sidebar). However, such sion, this article presents possible approaches exotic materials are currently impractical to these challenges, ranging from the imme- because of political issues. Another possibili- diately practical to the fanciful. However, each ty is to use primary chemical batteries, which idea is fashioned from practical issues and are relatively long lasting compared to applications in the field. rechargeable ones. However, large-scale adop- Each of these issues is closely related to the tion would result in serious environmental others, and a design change to correct deficits disposal issues. in one often affects the others. The most imme- The obvious alternative is secondary bat- diately striking challenge is in creating appro- teries. However, rechargeable batteries require priate interfaces for wearable computers. that the user remember to maintain them, However, the issues of power use, heat dissipa- which can be a problem. For example, digital tion, networking, and privacy provide a neces- phones with multiple days of battery life still sary framework in which to discuss the interface. run out of power—often because users forget to charge them. For wearable computers that Power use are part of a wearer’s everyday life, recharging Power is perhaps the most limiting factor the batteries should be tied to everyday in mobile technology. Although transistor actions. The user needs to create a daily rou- density continues to shrink exponentially, bat- tine that includes computer maintenance, tery energy density, whether measured by vol- similar to cleaning contact lenses or eyeglass- ume or by mass, increases linearly with a es. For example, designers could make a com- relatively shallow slope. A mobile device’s mass puter with 16 hours of battery life that would is often determined more by its power source recharge in the eight hours that the user sleeps. than the underlying electronics. Given the Other natural breaks that could provide continuing financial costs and design con- recharging time are at meals and at the begin- straints of advanced energy technologies, a ning and end of the workday. small-device designer is well advised to deter- Ideally, recharging the wearable computer mine the maximum allowable cost, size, and and its peripherals should be implicitly cou- weight for the battery before designing the pled with the normal acts of dressing. For electronics, functionality, and packaging. In example, an inductive charger hidden in the

JULY–AUGUST 2001 49 WEARABLE COMPUTING

inconvenient. If the soldier’s on-body elec- Pacemakers and power tronics used foodstuffs for its operation, the Pacemakers demonstrate a design extreme that general-purpose wearable computers do soldier could decide whether to eat the food or not generally address. The pacemaker example helps illustrate the complicated design choic- use it to power communications to his home es designers make in terms of power use in a wearable computer. Through electrical cur- base. Although certainly a fanciful idea now, rents, pacemakers regulate the beating of the wearer’s heart. Advanced pacemakers have work in robotics could make this feasible. computer-controlled components that monitor the wearer’s heart rhythm, breathing rate and Yet another alternative is to scavenge power depth, body motion, or muscle activity to determine whether the heart rate needs adjusting from the environment. For example, it is pos- (rate-responsive pacing). Some pacemakers even have external components that let a patient sible to recover an average of 50 W/m2 from or caregiver monitor the pacemaker’s status. These advanced pacemakers satisfy many def- rigid outdoor solar power panels aimed at the initions of wearable computers. sun (assuming a 20 percent efficiency con- Since pacemakers are implanted, there is a high penalty for replacing batteries or for con- version of a 250 W/m2 solar load). However, necting to the pacemaker’s circuitry for reprogramming. Exotic power sources such as lithi- flexible solar cells appropriate for use on cloth- um-iodide batteries and plutonium-238 cells minimize the need for reimplantation. In addition, ing have significantly less conversion efficien- medical personnel upgrade pacemaker software via electromagnetic couplers placed outside cy and would not always have direct sun the body. The pacemaker can also provide diagnostic information through these couplers. exposure. Available power would also drop Pacemakers could, in theory, be fitted with powerful transmitters and encryption systems significantly when a wearer stepped indoors. to communicate their information securely through today’s cellular phone infrastructure for In general, the main constraints of scaveng- easy access by medical staff to patient data and programming updates. However, the over- ing light to power wearable electronics are whelming emphasis on power limits such gadgetry. needing a large surface area on the device This trade-off is common in the more general field of neuroprosthetics. Designers in this devoted to recovering energy and aiming the field develop computer controls for artificial cochleas, artificial retinas, and deep brain stim- device toward a light source. ulators for the treatment of epilepsy and Parkinson’s disease. They remain alert for the effects Another possibility is to recover power from of new features on their devices’ power consumption and flexibility in adapting to future radio transmissions, as, for example, in the updates. crystal radio sets that hobbyists use to receive AM radio broadcasts. In fact, in most popu- lated areas, similar devices can recover milli- surface of the wearer’s bedroom dresser could watt-level power. Of course, just as with solar wirelessly charge electronics placed there— power, the size and direction of the receiving similar to setting down cuff links or eyeglass- antenna could make such a device inconve- es. Such systems seem feasible given the nient to wear. existence of similar home electronics such as However, imagine an on-body wireless net- inductive stoves and inductively charged elec- working system in which radio transmissions tric toothbrushes. Similarly, the act of placing from an on-body base unit provide power.9 shoes in a closet or a jacket on a hanger could Although only low-power establish wired or wireless connections and sensors could use such a system, the con- embedded in these items for recharging a cept of a combination wireless network and computer. centralized power supply is attractive. Passive Alternatively, some wearable peripherals radio frequency identification (RFID) tags could generate power from human actions or exploit a similar idea. A tag reader generates an from the phenomena they sense. For exam- electric field that the tag harvests for power ple, the energy expended in pressing buttons whenever it is brought within range. When on a one-handed keyboard might power the the tag has stored enough power, it generates keyboard. One of the most intriguing possi- a unique digital radio signature that an- bilities currently being researched are shoes nounces its presence to the reader. that generate power from the wearer’s heel strike or bending of the sole while walking.8 Heat dissipation An esoteric but theoretically possible The companion problem to power use is heat method of powering on-body electronics is to dissipation. When specifying processors for use the same power source as the wearer—that wearables, MIPS per watt is a much more is, food. This idea could have military appli- important parameter than raw processing speed. cations where providing separate supply lines Power density of (the now older) 0.6-micron for the soldier and his or her electronics is microprocessor chips surpassed that of a kitchen

50 IEEE MICRO hot plate’s heating coil; the problem is only ple, when he or she enters an air-conditioned becoming more severe.10 Current desktop building. Temperature feedback mechanisms, processors can require over 100 W of power. already common in microprocessor design, Putting such a processor in a pocket-size device could be adapted for these tasks. would create the equivalent of wearing several More aggressive systems might employ high-power soldering irons. Given that devices thermal regulation via active thermal reser- in contact with human skin should not much voirs. For example, cooling systems could exceed 40° Celsius, using such processors would exploit the heat capacity of the computer’s bat- be extremely difficult in a small design. teries. While charging, users could chill bat- In fact, heat dissipation is one of the fore- teries so that the wearable computer could most limiting factors in the design of high-end transfer heat into them during operation. For , and providing heat dissipation is a some batteries, this warmth could increase source of considerable expense. Designs must battery life. In addition, by employing active channel heat away from the processor, or else cooling elements such as Peltier junctions, the it will suffer thermal shutdown. Of course, computer might cool the batteries or compo- manufacturers have made progress in making nents during times of low ambient tempera- processors tolerate higher temperatures, but ture. Thus, the computer would have access to according to a 1998 study, processors exceed- a thermal reservoir during times of heat stress. ing the 40-W range cost an additional US dol- Unfortunately, current Peltier device ineffi- lar per watt per chip.11 Current laptops use ciencies make this method impractical in the expensive heat spreaders and evaporative heat near future. However, a water reservoir, per- pipes to transfer heat to other surfaces of the haps stored in a sponge, could provide a heat laptop for radiative and convective cooling. Of reservoir through evaporative cooling. course, another solution is to make lower- Phase-change materials provide an attrac- power processors and components. tive method to compensate for lack of cool- Several additional alternatives could be fea- ing.12 Such materials can absorb a tremendous sible for wearable computers. With a wearable amount of heat while they maintain the same computer, the user’s thermal environment temperature as they transition from solid-to- changes routinely, often to the computer’s ben- liquid or liquid-to-gaseous phases. Thus, if the efit. For example, even a weak airflow can sig- wearable computer’s casing encapsulates such nificantly increase heat dissipation. While a material, the produced heat can be directed walking, the airflow about an arm-mounted into changing the phase of the material while computer is significantly enhanced by the arm’s the unit is turned on. When the unit is off, it pendulum-like movement. In fact, the airflow would cool, causing the encapsulated materi- along the forearm is turbulent in many situa- al to revert to its original phase. An ideal mate- tions, effectively doubling the heat dissipation rial would require a large amount of heat to of calmer air movement.6 Also, if the wearable change phases. It would also have its first phase computer is filled with nonconducting fluid change at approximately body temperature such as 3M’s FluorInert, movement will create and its second phase change at approximately currents that help transfer heat away from the 41° Celsius. In this manner, temperature processor to the computer’s packaging. plateaus occur at both a standard user comfort Another idea is to use the wearable com- level and the maximum allowable operating puter’s close proximity to the human body to surface temperatures. Although such a mater- aid in cooling. For example, a forearm-mount- ial probably does not exist, at least in a non- ed wearable computer could dissipate heat toxic form, combinations or stratified layers of directly to the user—a greatly appreciated sit- materials could prove adequate. uation in winter.6 This idea is not so unusual; Finally, careful use of resources might help a similar computer cooling effect already avoid many heat generation crises for a wear- occurs when users place modern notebook able computer. For example, developers could computers on their laps. In addition to exploit- write applications for wearable computers with ing changes in ambient and skin temperatures, heat dissipation in mind. The computer can the wearable might take advantage of the cool- delay disk maintenance, downloads, and batch ing effects of the user’s perspiration, for exam- jobs until it senses a cooler environment.

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4. A. Smailagic et al., “CMU Wearable Com- Further resources puters for Real-Time Speech Translation,” Proc. ISWC, IEEE CS Press, Los Alamitos, • http://www.cc.gatech.edu/ccg Calif., 1999. • http://www.media.mit.edu/wearables 5. T. Starner et al., “Augmented Reality • http://www.charmed.com Through Wearable Computing,” Presence, • For a complete bibliography for this article, visit http://computer.org/micro. vol. 6, no. 4, Winter, 1997, pp. 386-398. 6. T. Starner, Wearable Computing and Con- text Awareness, doctoral dissertation, Media Depending on perceived user need, a slower Laboratory, Massachusetts Institute of Tech- network connection might be appropriate to nology, Cambridge, Mass., 1999. allow more time for heat dissipation. With 7. E. Post et al., “E-broidery: Design and Fabri- such methods, performance is reserved for user cation of Textile-Based Computing,” IBM Sys- interactions, and the effective average power tems J., vol. 39, no. 3, 2000, pp. 840-850. consumption can be higher without causing 8. J. Kymissis et al., “Parasitic Power Harvest- uncomfortable spikes in heat generation. ing In Shoes,” Proc. ISWC, IEEE CS Press, MICRO Los Alamitos, Calif., 1998, pp. 132-139. 9. E. Post et al., “Intrabody Buses for Data and Acknowledgments Power,” Proc. ISWC, IEEE CS Press, Los Thanks to the Spring 2001 Mobile and Alamitos, Calif., 1997, pp. 52-55. class at the Georgia 10. S. Borkar, “Design Challenges of Technolo- Institute of Technology, which field-tested gy Scaling,” IEEE Micro, vol. 19, no. 4, 1999, many of this article’s examples and its more pp. 23-29. esoteric ideas. Thanks are also due to the 11. V. Tiwari et al., “Reducing Power in High- Georgia Institute of Technology Contextual Performance Microprocessors,” Proc. Computing Group, the Massachusetts Insti- Design Automation Conf., ACM Press, New tute of Technology Wearable Computing Pro- York, 1998, pp. 732-737; citeseer.nj.nec. ject, and the members of wearables list. In com/375008.html. particular, Brad Rhodes, Lenny Foner, Rob 12. N. Leoni and C. Amon, “Thermal Design for Melby, Kent Lyons, Dan Ashbrook, John Nis- Transient Operation of the TIA Wearable sen, and Chip Maguire contributed their time Computer” Proc. ASME InterPack, vol. 2, to help guide structure and provide details and Am. Soc. of Mechanical Engineers, New references. York, 1997, pp. 2151-2161. This article is dedicated to the memory of , hacker par excellence. Thad Starner is an assistant professor at the Georgia Institute of Technology. His research References interests include intelligent agents, wearable 1. B. Rhodes, Just-In-Time Information Re- computing, , and pattern trieval, doctoral dissertation, Media Labora- recognition. Starner has a PhD from the tory, Massachusetts Institute of Technology, Massachusetts Institute of Technology Media Cambridge, Mass., 2000. Laboratory and has been wearing general-pur- 2. G. Kortuem, Z. Segall, and M. Bauer, “Con- pose computers as part of his daily life for text-Aware, Adaptive Wearable Computers eight years. He is a member of the IEEE as Remote Interfaces to Intelligent Environ- Computer Society, the ACM, and the AAAS. ments,” Proc. IEEE Intl. Symp. Wearable Computers (ISWC), IEEE CS Press, Los Direct questions and comments about this Alamitos, Calif., 1998, pp. 58-65. article to Thad Starner, Georgia Institute of 3. S. Mann, “On the Bandwagon or Beyond Technology, College of Computing, 801 Wearable Computing,” Personal Technolo- Atlantic Dr., Atlanta, Ga. 30332-0280; gies, vol. 1, no. 4, 1997, pp. 203-207. [email protected].

52 IEEE MICRO