Scratch Board guitar

Wandering through the MAKE Flickr pool the other day, I saw what appeared to be custom-made game controlling guitars. Taking a closer look, I saw that they were actually using Scratch Sensor Board controllers. The Scratch Board is a neat device with four inputs for custom built sensors. On the board itself are a potentiometer, light sensor, sound sensor and a push button. Your program can look for user generated input on each of these, which can change your program or game based on the sensor input.
Chris, whose photostream the picture was in told me a bit about the project: