Andy, I would go with a stand alone GPS. I have a original droid with copilot on it as to store the maps locally on the phone if you lose your signal. No signal/no maps unless you use additional software on the phone. That being said, a standalone rugged GPS will last you a long time, if you have to cross a river or fall off a boat and are swimming, they are waterproof and durable against dropping them but the beauty of them is they store electronic maps of the entire world and they use common batteries and can be ran 100% off of a solar cell.

I can't run my Droid off a cell 100%, the minute I pull my battery out of the phone and boot up, the software of the phone will not allow me to run the phone with no batteries in the unit, my GPS will. Essentially as long as you have a sun you have navigation and if we ever lose all the satellites for the GPS, you still have very good quality maps on you of the entire world.

With the GPS map data base alone, if you are traveling, flying, sailing, or what have you, you are carrying maps on you at all times, not to say I don't carry a compass and paper maps as backup.