Incase, makers of various addons for the iPhone, introduced the Power Slider on Monday, a new protective case designed for the iPhone 3G, and will retail for $99.95. It’s coming in time for the holidays (listed as due to be released on the 28th of this month right now), and will be available at the online Apple Store and Apple retail stores.

The Power Slider features an internal battery that can more than double the battery life of an iPhone 3G, according to the developer. It sports a custom-designed lithium-ion polymer battery that provides continuous charge to the iPhone’s own battery. When in use, the Power Slider’s battery drains first before the iPhone’s battery is used at all. Terrific case for those constantly on the go.

The Power Slider integrates a five-light LED battery status indicator; it also shows sync mode and charging status. A custom USB cable is included that enables you to charge and sync data with your computer.

The Power Slider is also a functional iPhone case, featuring hard-shell protection. It’s an adaptation of Incase’s Slider case, equipped with a “soft-touch” coating to improve grippage and feel.

Incase rates the Power Slider as providing up to 330 additional hours of standby time for the iPhone, up to 26 hours of additional audio playback, and up to 5 hours of additional talk time on a 3G network (10 on a 2G network). Sales are predicted to be brisk.