I picked up a PLX Kiwi Bluetooth OBD II reader for my '05 MCS. I then added the Torque app to my HTC Evo. It is soooo fun. I can read data, clear codes, monitor boost and a million silly things I never thought I would care to know.

I really got this thing to compensate for the lack of temp gauge in the car. I also needed a digital speedo. My speedometer is partially blocked by my steering wheel and when I can see it, it reads 5 mph off at all speeds.

I can have all my relevant gauges on one screen. I have a giant speed readout a swipe away. One more swipe and I have a digital readout of my coolant temp. This is so cool.

 

That's pretty sweet!