I had an app called HandyLight that let you use 3G tethering without paying AT&T's extra monthly fee. When I upgraded to the iPhone 4S from the iPhone 4, the .

I had an app called HandyLight that let you use 3G tethering without paying AT&T's extra monthly fee. When I upgraded to the iPhone 4S from the iPhone 4, the .ipa wouldn't install. Even when I tried to add it through iTunes, it would immediately delete itself.