a) Turning the PC on when 'Unlock' signal is seen from the remote control keyfob. (And shutting down when the 'Lock' signal is sent)
b) Replicating the buzzer for things like PDC sensor, Cold temperature, etc.. (As I have removed the stereo and it used to do these functions)
c) Dimming the LCD display when the lights are turned on.
Admittedly, you could probably use the ELM327 to act as the interface but I was looking for a flexible development system.