I think that this is worth looking into. I know there is software out there to read OBD, but I wonder how much you can actually view, and modify with a PI, plus you could make your own GUI/Display.
http://www.stuffaboutcode.com/2013/07/r ... -data.html
The OBD 2 cable to USB is 6 bucks!
http://www.ebay.com/itm/VAG-COM-KKL-409 ... ls&vxp=mtr