Just got finished wiring up the GPS. My buddy came over with his Fluke multi-meter and we tested all the connections to verify power/ground/continuity/etc.... I used the BMW "test" plug and soldered it to the Garmin GPS supplied wire harness and heat-shrink wrapped the connections. The BMW test plug has (3) wires labeled 1, 2, & 3. 1 is ground and 3 is positive. I cut the Garmin wire harness and spliced in an SAE plug between the voltage reducer and Mini-USB that plugs into the back of the GPS. I also soldered and heat-shrink wrapped those connections. Now, I can leave the GPS wire harness with fuse block and voltage reducer permanently plugged into the BMW GPS connector on the bike and when I remove the GPS from the bike I can just disconnect the SAE plug and the Mini-USB comes inside along with the GPS and the SAE plug just gets a cover installed on the bike and is weather proof. VIOLA!!!! I'm set now
BTW... as previously stated the power coming from the BMW GPS plug is 12V so if your GPS requires less than 12V be sure to use the voltage reducer or you will fry your GPS.