AT&T Locker app now lets you store your Windows Phone 8 content in the cloud
Not only is your content stored safely by AT&T, it can be accessed from your phone or computer. You can use either a Wi-Fi connection or an AT&T cellular connection while storing or retrieving content. And while the app is just now available for Windows Phone 8 models, it also can be used with the Apple iPhone 3GS and higher, and on phones running Android 2.1 or higher.
source: AT&TLocker via WMPoweruser