Mogees is a gestural touch interface system developed by Bruno Zamborlin.  It works with any contact microphone and rigid surface.  The actual resonance of the surface affects the sound, plus the system recognizes the kind of contact the user is making (tapping, scratching, slapping etc.).   In other words, it can turn just about anything into a hybrid digital/physical instrument and an innovative touch interface.  Watch the video for examples, including some cool echoey effects from a balloon.