>seems kinda obvious to me, but why not use the serial port?
>Seems like that would be the easiest thing to hack,
>rather than screwing the the mic or other input line.

Yes, just using a pin off the serial port would be easier for me, but there are tons of third party in-car projects/addons that use the serial port, and I wouldn't want any conflict with those(GPS, Palm, remote controls, ..).

Right now I'm leaning towards connecting one of the serial port output pins (eg. TXDATA) through a resistor to the MIC input. That way, I could just have Hijack toggle out a bit or two on the serial during boot, and take MIC samples to see if the two are connected. If done right, it might not even interfere with in-home use of the microphone (assuming the output pin chosen can be avoided during "normal" serial port usage).

-ml