At TechFest this year I met with Desney Tan
and Dan Morris
me several very interesting systems, each of which allows your body to become the input device for hardware. Granted, this hardware was literally put together with tape and exposed wires (that just increases the cool, IMHO), but this proof of concept worked
incredibly well considering its fragility. Also, Desney really could use a metronome and some time spent practicing Guitar Hero.
Dan showed us how we might interact with devices by using our body as a control device. By tapping in a specific area on your arm you are able to navigate, read email, or play games.