New version of Android brings "Doze" Feature which shuts down processes in certain apps to stem battery drain. Google is aiming to give your phones and tablets a little more juice to make it through the day without dying.
What Doze will do is recognize based on the movement of your device whether it is stationary and based on that information will "exponentially back off background activity to go into a deeper sleep state." The device will still be capable of pushing through real time alarms or respond to chat requests in this state, but background updates will be slowed or stopped.