A recent addition to the Interaction Design Encyclopaedia goes in deep in the topic of wearable computing. The article was written by Steve Mann, who’s been working in this field for decades.
“An important distinction between wearable computers and portable computers (handheld and laptop computers for example) is that the goal of wearable computing is to position or contextualize the computer in such a way that the human and computer are inextricably intertwined, so as to achieve Humanistic Intelligence – i.e. intelligence that arises by having the human being in the feedback loop of the computational process…An example of Humanistic Intelligence is the wearable face recognizer (Mann 1996) in which the computer takes the form of electric eyeglasses that “see” everything the wearer sees, and therefore the computer can interact serendipitously. A handheld or laptop computer would not provide the same serendipitous or unexpected interaction, whereas the wearable computer can pop-up virtual nametags if it ever “sees” someone its owner knows or ought to know.”
Update (1/1/13): With the announcement of Google’s Project Glass earlier last year, wearable computing has got a lot more attention. Check out some more articles on the topic here: Our augmented selves: The promise of wearable computing, and Perpetually connected: Are wearable computers and bio-implants the future of mobile?.
Link: Wearable Computing (interaction-design.org)