I have an iPhone 3GS. It's a great phone, but the battery life simply sucks! I remember my old Nokia 6800 and its 10 day battery life. The iPhone is lucky to get a fifth of that. During busy days, I often can completely drain the battery before I get home. Because of this sad and simple fact, I always carry around my Scosche Flipsync keychain charge and sync cable in case the phone runs out of juice early. This works great unless I don't have my laptop with me.
After discovering the Arctic Cooling C1, it doesn't have to be. The Arctic Cooling C1 is a tiny USB battery pack with a reasonable amount of juice inside. Not only that, but it has a solar panel built in to keep the battery topped up.
The C1 is significantly smaller than my iPhone. It's tiny enough to keep in your pocket. Still, it has an 880 mAh battery (5V) inside as well as a small solar panel that can completely charge the device with 10 hours in direct sunlight. You can also charge via USB which can take from 1-3 hours depending on the USB port.
The C1's solar panel is useful if you're outdoors, but indoors it's almost useless. If you're on a camping trip and want to charge your USB device overnight, it can work. If you forgot to charge it yesterday and attempt to recharge inside, you might get a few minutes of charging. Stick with the USB charger if you want to use it inside.
The C1 can almost double my iPhone's life. This lets me use it all day and on days of moderate use I can get up to two days of iPhone use. This is often the difference between having no phone and having the internet at your fingertips.
The C1 comes with several tips. Unfortunately, the only one I had any use for was the mini-USB tip. It's convenient because the mini-USB tip is used to charge the device so you don't have to carry a spare around. The C1 plus my Scosche mobile iPhone cable is a great combo to keep me connected to the world. If you're looking for a device to keep you powered on the go, the C1 is an inexpensive and effective tool.