Globalsat BT-338 Bluetooth GPS Receiver
This little puppy works well. It takes up to 1 minute to acquire enough satellites to fix its location, so the TomTom software on my treo doesn't even acknowledge its existence until the green light starts flashing. But then it works like a champ. It has a long battery life and seems to be quite accurate in its location readings. After about six months, mine developed a problem with its power switch, but I used their web interface to fill out a problem report, got a timely response from their support engineer, and US Globalsat sent me a replacement within days.
This is pretty cool, leave it in the car, or take it with you. MINI approves :)
This runs great on the treo! TomTom is an excellent navigation system. I love being able to see where we are in real time and see what we are passing by as we fly down the interstate. (Not while I'm driving, of course!)
Free, easy, and FASCINATING!!!!