Via documented OBD mechanisms? Yeah, probably not much. Via a standard Bluetooth<-> CAN interface plugged into the OBD port? Lots can be done, because general

Via documented OBD mechanisms? Yeah, probably not much. Via a standard Bluetooth<-> CAN interface plugged into the OBD port? Lots can be done, because generally the OBD port will expose the main CAN network and once you reverse engineer whatever inter-module messaging the manufacturer is using, you can act as a real module (for example, the throttle pedal) and all sorts of Bad Things are possible. Here's a great write-up, which is also a good primer on automotive control reversing techniques for the uninitiated: http://illmatics.com/car_hacking.pdf http://illmatics.com/car_hacking.pdf