Wearable
computers come in many forms, but are generally considered to be any
interactive, wearable
device for
augmented reality or augmented
memory.
Pioneering research in this field comes from the MIT Media Lab, especially under the directon of Thad Starner and Steve Mann (independently). More information can be found on the MIT wearables page. It includes some perdy pictures and a nice case study.
http://wearables.www.media.mit.edu/projects/wearables/
See also, wearables node.