articles on hacking your vehicle bus
i put up a couple posts on my blog about hacking your vehicle bus... might be useful to those just starting out trying to determine how to interface with things like steering wheel buttons, door locks, windows/sunroof, stereo information, etc.
the posts use my 2003 Jeep Grand Cherokee as an example, which uses the Chrysler PCI Data Bus (SAE J1850 VPW protocol). everything should apply to those hacking on newer CAN-Bus vehicles as well - you'd just have to look at the datasheets i reference for the correct ELM AT commands.
i focused on how to use a laptop or tablet/phone to gather the information you need from the bus. once you have the info, you would then write an app for the laptop/tablet/phone or microcontroller code depending on your exact scenario. you could continue to use an ELM327 interface if you are working with a laptop/tablet/phone. if you are going to be using a microcontroller then you could still hack into an ELM based scan-tool (before the USB/Bluetooth interface portion of the circuits), but it would probably be simpler to just buy the correct shield or breakout board.