PowerSkin has released skins for the HTC Inspire 4G and HTC Desire HD, boasting 1500 mAh of power. PowerSkin makes cases with batteries built-in. Check out review of the PowerSkin case for the iPhone 4: PowerSkin for iPhone 4 Review
PowerSkins are designed to address both the power and protection issues consumers face. They are made of flexible, silicone rubber that protects against drops, and they feature XPAL Powered battery technology that extends battery life up to 8 hours. PowerSkins are rechargeable and 100% recycled (except for the battery and internal components). The collection includes skins for the iPhone 4, HTC Evo, HTC Thunderbolt, Droid X/X2, BlackBerrys and many other smartphones.
PowerSkins for the HTC Inspire 4G and HTC Desire HD are available for $59.99 on www.Power-Skin.com Amazon.com and a variety of online and brick and mortar retailers.