I've got a friend that takes camping/hiking trips that last up to a week at a time he got a 3000mah extended life battery for his phone and this charging deal http://www.zagg.com/accessories/zaggsparq.php
He goes an entire week without needing a power outlet so I'd say this is a winning combo.

Or you could try and do something crazy like getting a 12v dynamo (or putting 2 6v dynamos) on you're bike and hooking to a 12v power outlet (cigarette lighter style) and use a car charger to keep you're phone charged while you ride. I'm sure there'd be need for voltage regulators, capacitors or what not in doing this... But it would be cool.