Based on the no-longer-working luckylarry.co.uk
Now completely Open Source on GitHub.
A simple, minimalistic Arduino-based piano-theremin.
Needs a SRF05 sensor with Echo connected to digital pin 2 and Trigger/Init connected to pin 3.
Video:
Needs Arduino > 1.0-beta3 with the new UDP API (http://code.google.com/p/arduino/wiki/Arduino1)