here is some link for you:
Design:
The PIC-Key will be a one handed chorded keyboard similar in appearance to the Twiddler. It will connect to the computer via standard PS/2 mouse and Keyboard connectors. Users will be able to enter keys and move the mouse by pressing on a combination of 1 or more buttons. As far as the Host CPU is concerned, it will act just like commodity Keyboards and Mice; no special drivers will be required. The use of a PIC microcontroller will keep the overall component count low. I expect the most expensive piece to manufacture will be the plastic housing and switch assembly.
http://mudlist.eorbit.net/~adam/pickey/second one for you: only source with description and sch:http://www.piclist.com/techref/microchip/picboardasm.htmand last one sch and source :
http://www.sxlist.com/techref/ubicom/lib/io/dev/keys/picboard.htmor
http://www.piclist.com/techref/microchip/picboard.htm 
there are project with all you need
nice time
