I have an Infiniti G35 and really wanted to use GDCs joystick to steering wheel control but my motherboard had no joystick port and the USB joystick port did not work with his circuit.
What I did is connect a PAC SWI-X to the car and used the infrared receiver from my Radio Xtreme unit to control the computer. The setup is:
Steering wheel controls -> Pac SWI-X -> RadioXtreme -> Computer
I used the Rx commander software that came with the unit to control Frodoplayer. I now have buttons for:
1) Change to Frodoplayer
2) Change to CoPilot
3) Volume up/down
4) Track FW/REW
Since the PAC SWI-X unit supports many cars I think it is an easy solution for most cars.