Hacking Commercial GPS

I was wondering if this has been done before. I want to take a commercial GPS unit and provide the NMEA data to it instead of the reciever itself. Bassically I want the thing to function from a virtual environment.

Would the GPS receiver component be seperate from the OS and supporting components. I was thinking(like the modules) that mabye I can intercept a serial line from the receiver unit to the main processor.

Thanks,

Matt

I assume you want to modify the data that is comming from the receiver. Do you need the receiver at all?

Nope. If the receiver is seperate from the rest of the gps, I want to isolate it and send in my own data.