I recently bent this and thought I'd share it with y'all. There are details on the Get Lofi site under 'easy dub siren' which describes how to do this.
It is a very simple bend. There was only 1 resistor on the circuit board which I removed and replaced with a pot.
It has a jack socket added and a volume control. The two 'body contact aerials' are wired to 2 legs of the 'pitch pot'.
Feel free to message me if you want to know any other info.
Circuit Bent Sound Blaster Keyring. A.K.A. Dub Siren.mp4 (http://www.youtube.com/watch?v=w-58uWfuigo#)