For the iPhone users who have experienced short battery life (like when Wifi is turned ON) then this gadget may be the answer. It is certainly the best looking add-on battery I have seen for the iPhone.
//Jon
Via Macworld
Mophie Juice Pack Air gives iPhone longer run time by Peter Cohen, , Macworld.com mStation|mophie has introduced the Juice Pack Air for the iPhone 3G. It costs $79.95 and it’s coming this Spring. The ultra-thin Brenthaven Metrolite BP The Juice Pack Air is billed as “the world’s thinnest Apple-certified external battery for the iPhone 3G.” Inside is a 1200 mAH lithium polymer battery that can double the amount of time you have to talk, , listen to music or access the Internet.
The Juice Pack Air comes in a form-fitting hardshell case for the iPhone 3G. The case features a a pass-through USB connector that lets you charge and sync with iTunes. The case sports a four LED charge status indicator and an on-off switch; when off, the Juice Pack Air functions just as a case.
Mophie plans to make the Juice Pair Air available in black, white and purple.
link: Mophie Juice Pack Air gives iPhone longer run time | iPhone Central | Macworld