Doesn't sound so bad. Would come in handy when I go camping. At the moment I just switch my phone off but it also means I don't get to shoot video or check my emails or messages.
Last time I went hiking I couldn't be informed a relative was injured so... yeah.
I know there are solar chargers, a friend has one but they haven't been so useful in the UK!
A very high capacity external battery costs $40 - $60 and assuming you judiciously use airplane mode and don't use it as a TV every night should keep your iphone going for a week. Buy two of those and you will have still spent less and have less to carry and you can go crazy with your iphone over a week camping trip and you won't run out.

