Vivian Caccuri‘s Submersed Songs tracks the movement of four carp and uses that data to control an audio mix –

Submersed Songs is a sound installation that generates mp3 player remixes through the movements of four live fish. The animals’ movements and the proximity among them work as a parameter for mixing and spatializing the audience’s music tracks in real time.
This system constantly mashes-up two different songs recorded by different users. The two tracks are submitted to different modification processes, building a real time continuity between the swimming of the carp fish and the levels of distortion- which can vary from an intense reverberation to a simulation of hearing underwater.

I imagine a smaller version could be used to augment control voltages on a modular synth setup … hmmm. Submerged Songs [via Califaudio]

[Oh snap! Looks like Marc already covered this one awhile back.]