Battery drain. I keep my phone for emergency use.
Would it not be less expensive to purchase a secondary simple Nokia phone for emergency use?
This link seems to have some relevant info for using the iPhone for GPS tracking while backpacking:
http://adventurealan.com/iphone4gps.htm"When using an iPhone in shallow grade mountains or flat landscapes, with minor tree cover, the accuracy has consistently been within 15 meters. When using it in deep steep walled canyons, the fix is not as accurate as Garmin, 50 to 100 or more meters off in a deep canyon (Paria Canyon in Utah). Using a Garmin and an iPhone 4 we concurrently recorded tracks on 12 miles of trail in fairly dense conifers on the west slope of California's Sierra Nevada range and could not tell any difference in accuracy. "
"Our daily use of the iPhone includes 5-50 sessions with a mapping app (depending on how ambiguous the route is), 10-20 photos, occasional use of bird guide apps, alarm clock, checking time, reading Wiki Offline, and nightly journal entries. All of our usage is discretionary excepting for the mapping apps and GPS reads. We scale our discretionary use based on how many days remain before the next recharge opportunity. With restrained use, most models of iPhones (especially the iPhone6) will last for a week or even ten days."