The latest version of  Google’s mobile OS (KitKat) launched alongside Nexus 5, the newest handset is Nexus 5 and the second to be produced by manufacturer LG. KitKat has been optimized to run on a much broader range of devices, with special focus on the millions of entry-level devices that have as little as 512MB RAM. To help, new APIs have been created, better tools, and better documentation to let you create apps that perform well on all devices.


Check out this video summary of some of the most significant developer features in the latest Android release, including new ways to make your apps beautiful, NFC Host Card Emulation, a printing framework, the storage access framework, low-power step detector and step counter sensors, and more!

Google has reworked the UX, added in better support for low-end hardware, and tweaked many of Android’s core elements. 

Full Android 4.4 API Overview:
http://developer.android.com/about/versions/android-4.4.html