I've used iHike a lot over the last several years and I really like it. I use it for off-road trips and for hiking. I've tried some of the others but prefer iHike because I find it easier to use. It will plot your course on a topo while you hike or you can put in a route defined by way points in advance. The app is 5 or 10 dollars but there is no recurring charge or any charge for maps. You just need to be sure and download the USGS maps in a location where you have data coverage. I think you can also download USFS maps. If you don't have a map downloaded, it will still plot your course on a blank map which will allow you to retrace your route. I go on hikes with the app running for at least 8-10 hours and I still have some battery left at the end of the hike. I do carry a battery pack in case I run out of juice, but I've never needed to use it.
