I have a rechargable
GlobalSat BT-338 GPS unit that I use with my laptop, pocket pc and my motorola q.
I use it with Streets and Trips 2007, Netstumbler (for wardriving), Google Earth Pro and Virtual Earth Mobile for my Motorola Q.
It's rechargable batteries gives it from 16 to 17 hours of use per charge. Plus it is small enough to carry in your pocket and you can get a car charger for it to keep it charged in the car.
Tip: To use the gps unit on more than one device at a time, I suggest using
GPSGate. I use 2 devices with mine simultaneously... my pocket pc loaded with Streets and Trips 2007 (windshield mounted) and my laptop running Netstumbler for wardriving. It also allows more than one piece of software to use the gps signal too. This is nice for like running Netstumbler, Streets and Trips and Google Earth Pro at the same time.
Enjoy!