Martin got inspired by another guy doing a similar project using a Raspberry Pi and OBD-II reader on a motorcycle. So martin got a Pi and and a USB OBD-II reader on the cheap and got it working on his car. Seeing how the Pi is doing the heavy lifting here I can see a good start to a Car PC that monitors the vitals of your car, and possibly throwing in some multimedia and / or a touchscreen.
Martin has made his fork of the code available here and a little bit of instructions here. The decoding is done in python so it should be pretty easy to modify or add a PyGTK library for some graphing.