How to get a bool if device camera is hidden/returns black pixels

Hi everyone!

I'm actually working on a project with cardboard and I can't use my smartphone's compass. I saw a VR app where we could hide the device camera to move and I want to do the same.
There is not that much doc about it but I think I need to use WebCamTexture.GetPixels and check if returned pixels are close to black.

Is there a better way to do it?

Thanks!