OnBecameInvisible is called when the renderer is no longer visible by any camera.

This message is sent to all scripts attached to the renderer. OnBecameVisible and OnBecameInvisible is useful to avoid computations that are only necessary when the object is visible.

	// Disables the behaviour when it is invisible
	function OnBecameInvisible () {
		enabled = false;
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnBecameInvisible() {
        enabled = false;
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnBecameInvisible() as void:
		enabled = false

OnBecameInvisible can be a co-routine, simply use the yield statement in the function. When running in the editor, scene view cameras will also cause this function to be called.