[Teckjunkie] was inspired by Hack-A-Day to build a bio-interfaced game. He modified a thinkgeek pong kit with an Analog Devices instrumentation amplifier and differential electrodes to create biopong. Flexing either arm actuates the inputs on the pong game. (Now you can just grab some dumbells and get a pong workout.)
Hack-A-Day inspired projects are always welcome to the tips line.