You could check out the product line at PAC (anyone have that link again?) which includes an interface for various vehicles which will turn the steering wheel buttons into IR remote signals, allowing you to use aftermarket stereos with your steering wheel controls.

Better yet, remember that the Empeg, even when docked in the car, has a serial plug in the back.

OK, I know I'm new to this, but isn't there a mix in connections? I don't exactly understand how to connect an IR port to a serial port.