I recently saw a post about Leap on reddit, and started looking into it. Basically it gives you full 3d high resolution hand tracking on the cheap. Looking around the site I saw that you can apply to be a developer for it, so I started thinking of what kind of software I'd like to see with this thing.
Side to side motion with the left hand would select which channel you are working on. You could twist the right hand like you were turning a knob to affect volume, side to side motions to crossfade, live synth control like a theramin. The possibilities are endless with fine 3d control.
I can't wait to get my hands on one of these and start coding (assuming I get into the dev program)! Too cool!