Mugen Power is reported to be working on external casing for Windows Phones
From WP Central:
From WP Central:
Said cases would wrap around the handset to provide extra battery juice in emergencies when a power outlet is nowhere to be found. A jacket is to be produced for the Nokia Lumia 920 and HTC 8X, while a different solution is planned for the Lumia 820 (since it sports interchangeable covers). The company published a post on its Italy Facebook page asking those who are subscribed, "Do you have or plan to buy a Nokia Lumia 920, HTC 8X, 4 Nexus, Sony Xperia Z? Stay tuned, we will soon have news for you" (rough translation).Mugen working on Windows Phone 8 battery-extending products. Lumia 920 will get bigger.