From what I got out of his explanation, is that his prosthesis listens to the nerve signals that would control the muscles of a left hand (which he doesn't have). So, I think you could hook up a similar detector to your own arm for similar effects, its just that your arm would twitch along with your commands.

I suspect the reason we don't see these built for able-bodied people is that its easy to contact the fingers to buttons and knobs and read the muscle activations through these cheap, well-understood pieces of hardware. Might be slower than his input method though.