Just yesterday we got to share the exciting news that Android 4.2 was heading to the AOSP, and the factory images for the Nexus 4, 10 and 7-HSPA+ were made available. This is obviously awesome news for developers. Late yesterday Google went a step further to help out the devs in the community by making the Android 4.2 source code SDK available.
The SDK has some pretty cool support features. It includes support for the Daydream interactive screen saver mode, new lock screen widgets, multiple user accounts, secondary displays and much more. Also, don't forget that this new version 4.2 of Android also includes a host of cool features as well, like Miracast screen sharing, gesture typing, a new panorama photo feature called Photo Sphere and a quick settings pull-down. Very slick!
Source: Android Developers Blog