I'm interested to know how many of the apps I have installed are using GCM. Is there a way to find out?
Settings -> Applications, in the permissions section, tap on
Show All and under
Network Communication there should be
Receive data from internet if the application has requested push (GCM) permission.
Tested on 4.1.2, labels and positions may differ.
You could try Greenify. It's an app for hibernating apps so that they don't take up a lot of resources; thus, improving battery life.
However, it also lists apps in a way that lets you see which ones support GCM.