Oculus presence signal

Some games need to run both with Oculus as well as just on screen without an Oculus. A Rift presence signal is necessary in that case.
I checked the reliability of: isHmdPresent, which is a public static in the OVRmanager. (I checked withe the new Rift)
I made a very simple script that continuously looks at this signal. The result is always zero, so I can't use it.
Anyone who knows a more reliable signal for detecting the presence of the Rift ?

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class OculusDetect : MonoBehaviour
5. {
6.     public bool presence;
7.  
8.     void update()
9.     {
10.       presence = OVRManager.isHmdPresent;
11.      }
12.  
13. }