With a new case/batter combo called the Power Slider Case, Incase promises to more than double the battery life of the iPhone 3G. And, unlike other such solutions we've seen, the Power Slider doesn't appear to completely ruin the aesthetic appeal of the iPhone.

According to Incase, the Power Slider sports an optimized power management system for its Lithium Ion battery to provide a continuous charge to the internal battery of iPhone. When in use, power drains first from Power Slider so that the device's internal battery remains fully charged and is only depleted once the battery of Power Slider has been drained.

Meanwhile, the Power Slider allows users to sync and charge their devices while iPhone 3G is attached, so you don't have to remove the smartphone for these purposes. A five-light LED battery status indicator gauges battery life and denotes sync mode and charging.

Incase plans to ship the Power Slider in time for the holiday season. It'll go for $99.95.