Artist Simon Morris outfitted a skateboard with various sensors that convert acceleration, turns, and vibration into data that's wirelessly transmitted to a laptop. The computer than translates that data into sound, generating an "acoustical map" of the city being thrashed. From the description of the project, titled Musique Concrete:
Tricks and movements generate real-time sounds allowing the skateboarder to composes his/her soundtrack of the city. Furthermore, combining tricks and movements result in unique and often unexpected musical compositions. Used in conjunction with ramps, obstacles, ledges and other architectural elements that make up the skateboarder's universe, Musique Concrete provides the listener with a sonic imprint of the urban environment.
Link (Thanks, Dave Gill!)
UPDATE: Scott Underwood says, "This is quite like a project by South African artist Cobi van Toder called Skatesonic. It was shown at the ZeroOne San Jose ISEA2006 Symposium. Van Toder was was an artist-in-residence last year at IDEO, and we developed the electronics and board with her." Link