Event when the Headset is locked/turned off

I needed to run part of a code when the headset is locked or turned off. My game is multiplayer and I need to communicate that the player has left immediately, and I can't find any way to do this. I've tried all the OVRManager actions but none of them work for locking or when I turn off the headset by pressing the power button.

Does anyone know how to accomplish this?