Carman was a good start/attempt for N8x0 series... I don't know how far anyone's got porting it to the N900... I don't know why they'd try to be honest with you. From a development point of view the amount of work required to port over the entire enlightenment engine (that Carman's built on), VS just building a new app from scratch just doesn't make sense.

So on that note Spenc3 and I have started the Carocell project; interfacing to obd2 is dead easy, as already pointed out... the tricky part is handling all the automatic setup/teardown of bluetooth, and of course having a nice flexible GUI system for handling and displaying that info.

At the end of the day the only really practical use is for reading trouble codes and clearing them, which is the most difficult part of an app because it requires you to do a bunch of binary comparisons and evaluations in order to determine exactly what's what. Anyways long and short of it is that there are people working on it...