thŕattle

Theremin is the 1st musical instrument designed to be played without being touched. The controlling section generally consists of two metal antennas to sense the relative position of the player’s hands. These sensors control audio oscillator(s) for frequency from one hand, and volume from the other. The electric signals from the Theremin are amplified and sent to a loudspeaker. more >>

Performance by Pamelia Kurstin at TED:

Update #0: I’m getting an idea. Probably the same principle be used in Burglar Alarms. Might help catch thieves who aren’t perfectly insulated. >:O)

Here is Rommy:

And Chirpy:

Get yours from here & there.