SmartGlass will sync with a players Gamertag. As seen in the presentation at the conference, the app will provide additional info about the game or the video you're playing or watching.
Spencer described for games that will make special use of SmartGlass, “It just makes so much sense for a developer who wants to supply, maybe not time-critical information, like ‘that enemy is getting ready to shoot you,’ but information that augments what’s happening on screen."
He went on to describe how it might be used with Microsoft's upcoming third person beat'em up Ascend. “You’re even going to see situations like with Ascend, where there’s actually gameplay that happens on the phone, even when you’re away from your television and that interacts back with the online game that’s happening."
SmartGlass will be intuitive. “You don’t have to log in and out of each app – you know, ‘I’m gonna start the Mass Effect app, and now I’m gonna start the Game of Thrones app.’ So you have this surface, this smart surface that sits on any device that you already own that’s always in sync with what’s happening on the television, and it knows where to go and grab the right content to display at the right time, to make sure that if you’re playing Halo, then the Halo surface is available on SmartGlass,” Spencer boasted.
The other function of SmartGlass will be to link devices and the Xbox 360, where players can, say, watch a movie on Netflix on their tablet, stop, then pick up when the player left off on the 360.
SmartGlass will support Windows 8, Windows Phone, and "other" portable devices, though they have yet to be revealed.