Gesture control without a camera. Does it involve hacking a theramin? From the Wikipedia article:<p><pre><code> It is named after the westernized-name of its Russian
inventor, Léon Theremin, who patented the device in 1928.
The controlling section usually consists of two metal
antennas which sense the position of the player's hands
and control oscillators for frequency with one hand, and
amplitude (volume) with the other, so it can be played
without being touched.</code></pre>