>I suppose I could have it recognize NMEA strings coming in...

Wow, this would not even make life easier than to solve a problem with not enough serial ports on the empeg. You have a one-way-communication at 4800bps from the gps-mouse, so there might be enough space (it sends once a second) to control the empeg or (in further versions) sends a command from the car like "everything's ok" => www.ross-tech.com.

But this is future... Though, if it's not too much work, it would be perfect.

Rolf