If you have a Garmin GPS you can link their latest MapSource software to the TR1 via the Garmin data cable, connected to a serial to USB cable. Garmins, for some reason are all serial.
I have a Garmin V on my dash that I can link via the cables to the TR1 and it gives me real time locations. You can load detailed map info from the Mapsource CDs (topos, cityselect, etc.).
The nice thing about this setup is that you can use the GPS by itself or with the computer. If you get the other add on, its computer dependant (I believe).
Thats my take. 8)