This was the first time I used the GPS on my iPhone for tracking and marking waypoints. I stuffed it in a pocket on the top of my backpack and I must say it worked quite well. I used the iPhone app Trails to record the hike. The battery life was great, it only used about a third of the battery for the 3 hours it was tracking. One nice feature was the use of the light sensor (near the ear piece). When it was covered, the screen automatically shut off to help save the battery. The accuracy seemed quite good as well, there are even posts saying the phone/app bests a $200 Garmin.
Here are some pictures from our hike on the Merryman Trail at the Loch Raven Reservoir in Timonium, Maryland. We parked on Warren Rd. and had easy access to the trail. We got side tracked at the feeder stream waterfalls and took the fire road up to a neighborhood and decided to turn back (as you can see from the maps). Overall it was a nice hike and beautiful spring day. You can view more details on our Hike In and Hike Out @ EveryTrail.com.