The X-Power 1 is no different from a regular USB cable for you iPhone or the iPod but with the only difference of a small battery pack integrated into the cable. So charge the cable alone and use it to boost your iPhone / iPod battery later…
The manufacturers claim that this can allow you over 4.5 hours of talk time to your iPhone! Though if you are a regular battery hog you a battery pack is recommended, this is certainly something I would carry while travelling as it doubles up as a usb cord and costs just $30! Different variations are available in terms of size and design.
This should go on sale sometime soon!