Mophie (http://www.mophie.com) has released the juice pack air for the fourth generation iPod touch. It’s an US$49.95, thin, rechargeable battery case.
It packs a 1000mAh rechargeable lithium polymer battery that purportedly offers up to 34 hours of audio playback or up to 6 hours of video playback. The juice pack air delivers protection from bangs, bumps and drops. It has a soft-touch rubberized finish in black.
The juice pack air case will charge the iPod touch in approximately 100 minutes (assumes juice pack air case is full and iPod touch battery is at 20%). The included USB cable enables you to simultaneously charge and sync your iPod touch to iTunes without having to remove it from the case
The juice pack air features a toggle switch allows for standby and charging mode, so you only have to use the juice pack air battery when you need it. An integrated LED status indicator tells you exactly how much “juice” is left and also displays how much time remains during the charging process.