Well hit the trail for my first GEO hunt only to find that the IPhone 3GS is real poor on battery so pack a charger, I have an external battery pack for mine so I suggest you do the same or you will find the battery is good for about 45 min of use because it uses not only the GPS but also the 3G network to update the screen. Keep in mind the 3G Data as well or you may get a surprise bill, I have a 6gig plan so no worry for me.