The interface for the GPS is NMEA 0183, isn't it? So then, if one can add a second device for NMEA Input, it should work, I guess. I have the Y-cable for the GPS puck, which provides 4 pins, which I suspect are 12 V, GND, NMEAN in and NMEA out. It's from the original bus connector, basically the two voltage pins and the two pins in the middle... Is there a pinout for the second plug on the Y-cable?