I I have gps service on my nextel i580, while driving, even though it is slow, it seemed to be accurate. We started using it geocaching. My i580 was about 200 yards off. We quickly made a dash to our local mega discount retailer and purchased a Garmin nuvi 205w. Battery life is about 3-4hrs, and it is follows you very quickly. Most important it seems to be accurate. It has 3 modes, 1 automobile, 2. bicycle, 3. pedestian. I found a little program called EasyGPS on the geocaching web site where I can download several different caches review them and send them to my favorites on my gps.