Just got back after spending 3 days in the breaks.
I use Hunt onX app and it works great. Download the maps in advance. Turn off wifi, bluetooth etc and turn on offline maps option in the app. I believe you can also shut down the phone's attempting to find service, but I didn't. Only time it really ate batteries was when I turned on the tracking. Otherwise it was fine. I had property ownership, topo, sat image, government lans etc. Can overlay hunting districts, etc.
I typically shut the thing down for a majority of the time anyway and that helps also. I did have a couple small battery packs, about the size of a roll of lifesavers as a backup.
With all that said, I am considering buying a gps to pack and use as they are a lot cheaper if you break or lose it. Then I would have the iphone packed away securely as a backup.
