Avoid from being killed

Foreground process
A process that is required for what the user is currently doing. A process is considered to be in the foreground if any of the following conditions are true:
It hosts an Activity that the user is interacting with (the Activity's onResume() method has been called).
It hosts a Service that's bound to the activity that the user is interacting with.
It hosts a Service that's running "in the foreground"—the service has called startForeground().
It hosts a Service that's executing one of its lifecycle callbacks (onCreate(), onStart(), oronDestroy()).
It hosts a BroadcastReceiver that's executing its onReceive() method.
Generally, only a few foreground processes exist at any given time. They are killed only as a last resort—if memory is so low that they cannot all continue to run. Generally, at that point, the device has reached a memory paging state, so killing some foreground processes is required to keep the user interface responsive.




http://stackoverflow.com/questions/2785843/how-can-i-prevent-my-android-app-service-from-being-killed-from-a-task-manager

You can write a helper app to receive android broadcast"android.intent.action.PACKAGE_RESTARTED",when your app got killed,your helper will receive that broadcast and you can restart your app or whatever.
That's how 'Smart App Protector Free' do.
The bad thing is users must install two apps instead of one.