If you own an iPhone 3G, you know how the 3G and GPS features eat battery life. The Mophie juice pack is the first accessory I got for mine. I liked it, but like all juice packs, you'll have to plug it in at some point--unless you get the SoliCharger from SoliLight.
This new juice pack for the iPhone (both versions) and iPod is probably the most versatile in terms of how it gets recharged.
The SoliCharger can be charged in any one of four ways: via Apple's USB charging cord, an Apple compatible car charger, a computer's USB port, or directly from the sun.
When plugged in, the SoliCharger takes about two hours to fully charge, and when left under the sun, it takes about four hours. It can also be charged with the phone is attached.
The SoliCharger weighs only 1.4 ounces and features a lithium ion battery pack that can provide another 50 percent iPhone charge (about a few hours of use).
The accessory is available now for about $40.