A No-Touching 3D Computer Interface
Justin Schunick points out a video demonstration of a 3D input system which senses the user's hand position, but without requiring the user to touch a controller or wear a trackable position indicator. From the provided description: "Utilizing the theory of electrostatics, we have designed a low-cost human-computer interface device that has the ability to track the position of a user's hand in three dimensions. Physical contact is not required and the user does not need to hold a controller or attach markers to their body. To control the device, the user simply waves their hand above it in the air."
"...the user simply waves their hand above it in the air..." These are not the droids you're looking for.
... then maybe a no-touch interface is not going to work well for me. I found the Theremin to be almost impossible to play because there was no way to get my hand in exactly the same x-y-z coordinate and with the same roll-yaw-pitch attitude (all of which affected the frequency of the oscillator). YMMV, of course.