Brad
Arduino is a microcontrolle r. It's fully programmable with analog and digital inputs/outputs. So if you can wire it and program it, you can do damn near anything with one. There is one project doing batchfire/waste spark on a 4 cylinder car. All out of a $10 board.
Basically mine is going to read the gm flex fuel content sensor, send the values to a display (like a gauge), and possibly convert the signal (hz to volts) and spit out a 0-5v to my logger.