On my last holiday I took my iPhone into southern Tunisia for a trip across the desert. To keep it juiced up and protected I used two cool pieces of technology: a powermonkey eXplorer and The Ultimate iPhone Sand/Sea Case.
The powermonkey eXplorer is a universal charger and battery backup that can charge from a USB connection, 110V/220V in most countries in the world and via a solar panel. Here's mine recharging in the Tunisian sunshine.
Once recharged the little battery can be used to charge any device through the collection of tips that are provided. Or you can skip the battery if USB or mains power are available and charge your device directly.
The Ultimate iPhone Sand/Sea Case
To protect my iPhone I used The Ultimate iPhone Sand/Sea Case AKA a ziploc bag. The ziploc bag protected the phone from sand damage and kept it dry when I took it in the bathroom with me.
And you can use the phone without removing it from the bag. Here it is in action:
PS Yes there was cell phone service in the desert.