The aforementioned device has it's own site, as well, at:http://www.footmouse.com/
The best avenue for finding more information on this sort of thing would be to investigate assistive technology: technology that enables people with disabilities. Occupational and physical therapists, AT practitioners, special educators, etc. have been hacking together solutions like this for a long time, and a few eventually come to market.
On the other hand, when designing and distributing such things, please always remember people with disabilities. Some people may benefit more than you can imagine from your ideas and designs.