With all due respect for all the great opinions in this thread, but in a survival situation, battery life is an issue and from what I can see, the smart"er"phones are battery hogs.

I'm using an iPhone-4S and the first thing I bought was a Mophie Juice Pack Plus Case and Rechargeable Battery. It functions as both case and as an external battery that is always plugged into the iPhone. I keep a charging cable in the truck so I can top it up when I'm driving. Fortunately, it seems to be fine to leave these plugged in all the time.
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Better is the Enemy of Good Enough.
Okay, what’s your point??