Push notification vs Background daemon
There are two kinds of background daemon in mobile OS.
One is real-time background daemon, like Android and Symbian do. All application are running in real-time in background. The pro of this way is the application can complete tasks in background, for instance, completing a webpage downloading. And the con is, this keep running application will consume lot of electricity. A certain example is QQ for Android, which always running and consume almost half electricity.
And in iOS, there is another method to implement the background tasks. In this way, all notifications send to applications are pushed to a central place, where name is Notification Center. Then those notifications are push to system daemon on the device, and the system daemon wakes up the application and dispatch the notifications to them.
In this way, there is only one daemon is running in background and just need to maintain one heart-beat connection. It greatly saves electricity consumption.
For me, I think the way iOS undertake is much better than Android.