Interested developers can download the SDK here. It includes the Xbox SmartGlass Studio, which lets developers build SmartGlass actions; a SmartGlass JavaScript Library that contains device APIs to provide a consistent experience across platforms; and sample code.
Microsoft unveiled SmartGlass at E3, the annual gaming trade show. The feature promises to make your Xbox the center of any in-home entertainment experience. You can use it to push content from your phones and tablets to your Xbox 360 console, and vice versa. In addition to Windows 8 devices, Microsoft said it would develop apps for iOS and Android.
The potential for SmartGlass is much greater than just watching videos via your Xbox, however. With the right tools, game designers could integrate, say, your tablet into your game. For example a football game could display relevant stats with the main action on the screen, or a racing game could let you use your tablet as a controller.
Of course, that would require games to have built-in SmartGlass abilities, and Microsoft just took the first big step toward that happening with the release of the SDK.