I am looking for a history of research and technology in wearable
computer systems - a typical system would be one that includes a
mobile keyboard capable of high-volume text input, a head-mounted or
eyeglass display, and a PDA or other computer. The system needs to be
mobile, that is, while it does not need to be Internet-enabled, it
should be self-contained and not be tethered by a wire or be limited
by wireless range. The goal is primarily to input large amounts of
freeform text (examples are memos, poetry, magazine articles) while
walking around.

I am not primarily interested in commercially available devices, but
in a discussion of various approaches to this problem. What are all
the ideas of how to do it? What has worked? What are the problems?