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When I'm hiking, I don't really care where I'm going or where I've been, so I don't use them much. With that said, there is an excellent app called GAIA which runs on IOS devices and gives you deep details about your hike while overlaying good topo maps. You can download the maps so that they are available when you're phone is offline which is necessary to conserve batter power if you're going to be out for a while.