SmartGlass app will allow Windows 8 users to use their devices as secondary screens to interact with the Xbox 360 gaming console. A phone, a tablet or a desktop computer running Windows 8 could be used to access the Xbox dashboard, pause and rewind favorite movies, swipe, pinch, and tap to surf the Web on TVs.
The app will be included in the "Games" section of Windows Store and will be released with a freeware license. Future versions supporting Android and iOS devices are also in the works, according to Microsoft.
Source: Microsoft Blog