Interesting idea: The Human Body as Touchscreen Replacement. The downside to using a touchscreen over something with physical controls is that you lose that instant feedback of where the buttons are. (Skip a song on an old-school iPod while driving? Easy. Do the same on a touchscreen? That’s trickier.) Your own location sense plus knowing exactly what part of your hand (or, in another prototype, ear) you’ve touched could really improve usability for applications that are suited for it.