Turn Your Body Into Your I/O with Skinput
 

Electronic devices are getting smaller, and so are their interfaces. If you’ve ever had problems typing on your mobile, or changing a song on your iPod while jogging, Chris Harrison has the answer. His Skinput prototype is a system that monitors acoustic signals on your arm to translate gestures and taps into input commands. Just by touching different points on your limb you can tell your portable device to change volume, answer a call, or turn itself off. Even better, Harrison can couple Skinput with a pico projector so that you can see a graphic interface on your arm and use the acoustic signals to control it.

http://singularityhub.com/2010/03/04...skinput-video/