Tekkon has debuted the myPower leather sleeve for the iPhone and iPhone 3G. The case features a built-in rechargeable lithium-polymer battery that is claimed to double the battery life of the iPhone while ensuring that the external battery drains before the phone draws from its internal power. An integrated power-level indicator displays the charge status of the battery. Users can recharge both the case and iPhone simultaneously, using an outlet power adapter or a USB cable connected to a computer.

The myPower case is similar to the Mophie Juice Pack and Incase Power Slider, although the latter products offer hard-shell protection instead of leather.

myPower is priced at $70 and is expected to begin shipping in mid-December. The package will also include a myGuard screen protector.