Dave Rosenthal (former MIT/Sun/nVidia not archivist guy) and I talked a bit about gesture control when the first MEMS accelerometers came out. They allowed for a wide range of controls but they drifted horribly so it wasn't possible to do a sort of "hold for fast forward" kind of motion. You had to have a move to start and a move to end.
To some extent this is the same problem as the Leap which can know where your fingers are but you can't hold a gesture and move your hand (afaict, I've not seen the LEAP SDK in action yet)
This mode of input deserves to be used alongside other input methods such as keyboard, mouse, stylus/pen, various other sensors like gyroscope and touch screens.
No one mentioned this is a HN company?
Also the introduction video nicely showcases the possibilities.