BroadcastReceiver

Using BroadcastReceiver we can start app, service, or special code after mobile rebooting complete.

If mobile restart then all local app automatically force stop, as well as service also stop, But at the time of notification we need to process continue. That time BroadcastReceiver is very helpful.

Using BroadcstReceiver u can start service in background .

Follow i provide important link for that
http://ofps.oreilly.com/titles/9781449390501/Android_Broadcast_Receivers.html 

using this send sms
http://www.vineetdhanawat.com/blog/2012/04/how-to-use-broadcast-receiver-in-android-send-and-receive-sms/