Xbox SmartGlass has migrated over to Amazon's Kindle Fire and Kindle Fire HD tablets. First generation Kindle Fires are out of luck since they're based on Android version 2.3 and the Xbox SmartGlass app requires Android 4.0 and higher.
An update to Xbox SmartGlass little over a week ago made Microsoft's second-screen experience compatible with 7-inch and larger Android tablets. Xbox SmartGlass launched in November 2012, allowing Xbox 360 users to control videos and interact with SmartGlass-enabled apps and games using compatible smart phones and tablets. In addition to the Android app, Xbox SmartGlass is available for free on iOS devices and, of course, Windows 8 and Windows Phone.