I know there is a hack on the AVIC models to view ODB information on the screen, requires a cable that plugs into the OBD port and then into the USB port of the AVIC unit. Would think there would be a hack on other units with a USB port and running the WinCE platform.
AVICnet 2.1 for AVIC F series, working OBDII! Updated 04/18/12 - AVIC411.com
OBDII USB Car Diagnostic Cable - Black + Blue + Orange (DC 12V) - Free Shipping - DealExtreme
Now this would be cool: DashCommand
http://www.youtube.com/watch?v=xy6Mx9WQ8cY&feature=related