There’s a cool new project in the works called Velosynth, which uses magnets, accelerometers, and an Arduino micro-controller to turn your bike into a musical instrument. The project was recently posted onto Kickstarter and has already tripled their fund-raising goal in just a few days. Unfortunately they are all sold out of kits, but you can still make donations to the project here. Any donations of $5 or more will earn you a zip file of Velosynth recordings as well as a coloring book and crossword puzzle.
It would be cool to see something like this adapted to an RJDJ style iPhone/android app with customizable sound-scapes for the user to download and choose from.