DontGo (Diagnose on the Go), is an OBD scanner running on Maemo on Nokia N900 and developed using Qt framework.
At this stage supports KWP2000 since I have built to diagnose my Opel/Vauxhall Astra 1.4 2003.
Since USB interface on N900 is a bit of a hassle, i am using the ubiquitous ELM327 OBDII v1.4 Bluetooth Scanner, like this. The bluetooth in this device supports SPP (Serial Port Profile; an RS232 emulation over bluetooth). The elm327 commands are based on AT commands. The elm327 datasheet has got all the information required.
I had to use the rfcomm for Bluetooth communication on N900. The steps required to set it up were taken from this lovely post.
Adding more Models it should NOT be complicated since the interface structure and the comms interface are done.
If you want the source code let me know. However it needs to be rebuild before using it. The project still needs tiding up, so if anyone feels up to it that would be brilliant. Also if you need any guidance let me know.