A much better (in my mind) solution to your backpacking battery life issue is to carry a phone with a removable battery. If you're turning off all services including calls and SMS, there's simply no reason for the device to be powered on at all, and removing the battery guarantees there's not even a trickle of power being drained. For your alarm, well I assume you wear a watch backpacking, so you can use its alarm feature.
Of course, then you have the issue of finding a quality midrange or higher end phone with a removable battery in the first place. They are an endangered species due to the thinness war.
> Of course, then you have the issue of finding a quality midrange or higher end phone with a removable battery in the first place. They are an endangered species due to the thinness war.
I prefer external charging bricks -- if you upgrade your phone, you might need to buy a new cable with an external brick, but you are more likely to need a replaceable battery with a new form factor or output.
Of course, then you have the issue of finding a quality midrange or higher end phone with a removable battery in the first place. They are an endangered species due to the thinness war.