44Wearable computing can describe abroad range of devices and concepts. At thetime of this writing, wearables are generallyequated with head-up, wearable displays; one-handed keyboards; and custom computersworn in satchels or belt packs. Figures 1through 4 show members of the Massachu-setts Institute of Technology’s Wearable Com-puting Project with some of their wearabledevices. Unfortunately, the public often char-acterizes the field by its gadgetry instead of itsgoals. Ideally, wearable computing can bedescribed as the pursuit of a style of interfaceas opposed to a manifestation in hardware.This article develops goals and challenges forwearable computing, and promotes discus-sion in design techniques by suggesting meth-ods, albeit sometimes fanciful, of addressingthese challenges.What is wearable computing?Several authors have defined wearable com-puters by desirable characteristics. For exam-ple, Rhodes states that wearables provideportability during operation; enable hands-free or hands-limited use; can attract the user’sattention, even when not in active use; canrun continuously; and attempt to sense theuser’s current context.1 Kortuem et al. employsimilar criteria but use the term augmentedreality to describe “the user interface techniquethat allows focusing the user’s attention andpresenting information in an unobtrusive,context-dependent manner.”2 Meanwhile,Mann describes wearables as constant andalways ready, unrestrictive, not monopolizingof user attention, observable and controllableby the user, attentive to the environment, use-ful as a communication tool, and personal.3This article defines wearable computingthrough the effort to achieve a hypothetical,ideal wearable computer. Much of this phi-losophy reflects the concept of a cyborg or aman-computer symbiosis as introduced in1960. Manfred Clynes and Nathan Klineoriginally coined the term cyborg to describea human and machine combination where theinterface becomes a natural extension of theThad StarnerGeorgia Institute ofTechnologyWEARABLE COMPUTING PURSUES AN INTERFACE IDEAL OF A CONTINUOUSLYWORN, INTELLIGENT ASSISTANT THAT AUGMENTS MEMORY, INTELLECT,CREATIVITY, COMMUNICATION, AND PHYSICAL SENSES AND ABILITIES.MANY CHALLENGES AWAIT WEARABLE DESIGNERS AS THEY BALANCEINNOVATIVE INTERFACES, POWER REQUIREMENTS, NETWORK RESOURCES,AND PRIVACY CONCERNS. THIS SURVEY DESCRIBES THE POSSIBILITIESOFFERED BY WEARABLE SYSTEMS AND, IN DOING SO, DEMONSTRATESATTRIBUTES UNIQUE TO THIS CLASS OF COMPUTING.0272-1732/01/$10.00  2001 IEEETHECHALLENGES OFWEARABLECOMPUTING: PART1user. This interface would not require muchconscious attention, such as when a personrides a bicycle. Although Clynes and Kline’saim was adapting humans for the rigors ofspace travel, the same concept might beapplied to systems that assist the user on otherphysical and intellectual levels. J.C.R. Lick-lider expresses this in Man-Computer Symbio-sis where he defines the title term as…a subclass of man-machine systems.There are many man-machine systems. Atpresent however, there are no man-com-puter symbioses…. The hope is that, innot too many years, human brains andcomputing machines will be coupledtogether very tightly and that the resultingpartnership will think as no human brainhas ever thought and process data in a way45JULY–AUGUST 2001Figure 1. Wearable computing platformsworn by members of the MassachusettsInstitute of Technology’s Wearable Comput-ing Project. Photo by Sam OgdenFigure 2: Private Eye head-up display andsimulated view. The wearer’s visual system“shares” images from both eyes to createthe illusion that the wearer sees through theopaque display.Figure 3: MicroOptical’s display embedded in a pair of eye-glasses. The actual display is in the earpiece. An optical pathdeflects the image through the lens to a half-silvered mirrorthat reflects the image to the user’s eye. Photo by Sam OgdenFigure 4: Functional chordingkeyboard embroidered into ajacket. Photo courtesy ofRehmi Post and Maggie Orthnot approached by the information-handling machines we know today.Ideal attributesTo achieve the tight partnership suggested byLicklider, the computer must be a user’s con-stant companion. It must share the experiencesof the user’s life, drawing input from the user’senvironment to learn how the user reasons andcommunicates in relation to the world. As itlearns, the computer can provide increasinglyuseful and graceful assistance. Ideally, a wear-able should have several key attributes.Persist and provide constant access to informationservices. Designed for everyday and continu-ous use, the wearable can interact with theuser at any given time, interrupting when nec-essary and appropriate. Correspondingly, theuser can access the wearable quickly and withlittle effort. Such a device must be mobile andphysically unobtrusive.Sense and model context. To provide the bestcognitive support for the user, the wearablemust observe and model the user’s environ-ment, the user’s physical and mental state, andits own internal state. In some cases, the usercould provide explicit contextual cues to helpthe wearable in its task. To provide parity, thewearable should inform the user of its ownstatus, either through an explicit display orthrough subtle background cues. In addition,the wearable should make its models observ-able so that the user can identify misunder-standings and explicitly tutor the wearablewhen necessary.Adapt interaction modalities based on the user’scontext. The wearable should adapt its inputand output modalities automatically to thosethat are most appropriate and socially grace-ful at the time. For example, while attendinga meeting, the wearable could communicatewith its user through a head-up display. How-ever, when the user enters his or her car todrive home, the wearable could switch to anaudio-only interface. In many instances, thecomputer interface will be secondary to theuser’s primary task and should demand theminimal necessary amount of the user’s atten-tion. In addition, the interface should guar-antee privacy of interaction when appropriate,adapt to its user over time, and encourage per-sonalization of its interface.Augment and mediate interactions with theuser’s environment. The wearable should pro-vide universal information support in boththe physical and virtual realms. For example,the wearable should automatically gatherinformation and resources relevant to a par-ticular physical location and