Just weeks after first announcing its SmartGlass initiative for Xbox 360 at a pre-E3 press conference, Microsoft has released the SmartGlass software development kit. It allows Xbox 360 developers to easily integrate PC, tablet, and phone screens in with their Xbox 360 games and applications.

The SDK (Xbox 360 developer login required) comes with an Xbox SmartGlass Studio environment for building "SmartGlass Activities." It also includes a Javascript API that will work across Windows, iOS, Android and Windows Phone platforms, plus a library of sample code for developers to build off of.

At the E3 unveiling, Microsoft demonstrated SmartGlass for uses such as designing Madden plays secretly on a private screen, or managing player and weapon information during a Halo match. SmartGlass could also be used to navigate videos and movies being viewed on the TV screen, or to stream those videos from Xbox Live to a portable screen for further viewing away from the couch, the company said.

SmartGlass seems to be Microsoft's answer to the Wii U's upcoming tablet-equipped GamePad, and the service has some advantages over Nintendo's more integrated touchscreen approach. Besides minimizing costs by using touchscreen devices that players might already own, Microsoft says SmartGlass devices will also support features like "pinch to zoom" that are impossible on the Wii U's low-cost, single-point-of-contact tablets on the Wii U GamePad. Then again, the Wii U GamePad will be a standard feature available for every player using the console, while Xbox 360 developers will have to worry about supporting players that may not have a tablet or smartphone to connect with SmartGlass.

Microsoft's recently leaked (and still unconfirmed) roadmap for the Xbox brand highlighted SmartGlass-style features as key to increasing the system's "value proposition" in 2012. The company hopes it would do this by providing "synchronized rich client experiences across your TV, Phone and PC." SmartGlass is targeted for launch "later this year" according to Microsoft.