If you think your iPhone 3G could use more power then you need to get a MiLi Power Pack.

The MiLi Pack is compatible with the iPhone v1 and 3G. The power Pack gives up to 6 hours of conversation on the 3G version and 12 hours in 2G version, 6 hours of internet in 3G, 28 hours of audio reading and 8 hours of video.

One even will be able to connect and synchronize his iPhone to the computer without withdrawing the battery, the device cost just about $80.

GenMp3