airhurt, the bt-5 is an unbranded unitraq BT-5321R, it seems to have an issue getting a gps fix on my N800, but I created a small script that disconnects then reconnects to the device.. seems to fix the issue for me. I will try it with my 770 and see if it works.

another thing to bear in mind with that unit, it only comes with a car charger... but, since it's a mini usb connector(can't use it as a usb device), you can use a standard cable to charge from your computer, or if you have a power adapter(motorola phone, etc) that works, too.

also, I would just go to http://www.geeks.com under the gps section to make your purchase, bypassing the link above.