I've seen Fast and the Furious 26 times

Mike Harkabus over at Clarity Consulting has created a code example for Coding 4 Fun on using an accelerometer to measure the performance of your car.  No need to even modify your car, the USB accelerometer will handle it.

It polls 20 to 30 times a second and with this ability, one can measure acceleration, braking distance, and handling.  The article goes in far more detail and is worth checking out.