One-hand wearable keyboard with USB interface
The latest keyboard version is an evolution of older one which was based on ATtiny2313 and could be connected to PC via PS/2 and was based on Attiny2313 microcontroller. Latest wearable keyboard is ported to at90usbkey demo board and can be connected to PC via USB.
Keyboard is able to produce all usual characters with few keys that are pressed in groups. It may be convenient to use it on special conditions like for portable computers, palmtops and so on. If you want to study it more John W. McKown provides project files and compiled firmware for free.
The USB source code is free too as a *nix-style patch file which converts Atmel’s demo code for the at90usbkey board into avr-gcc/WinAVR C source for the one-hander. See chordite.com/news.htm
More modern pictures are here:
http://chordite.com/new_design.html