In the case of traditional phones such as feature phones, terminal manufacturers have incorporated a protection mechanism called "secret mode" or "privacy mode" in their phones by developing dedicated application software and dedicated content file formats as a set.
That said, if you snagged yourself a Rift dev kit and have no intention of actually developing games with it, the upcoming UDK release also includes a "VR Mode" version of the software's sample Unreal Tournament game, as well as a summer version of the Epic Citadel demo we were shown at CES 2013.