I do know that such a thing is possible, due to RoboRecall displaying a scoreboard on the Spectator Screen while someone else’s playing.
Leaving the UI for a Spectator Screen while the player itself has a totally clean view through his HMD would be extremelly beneficial to VR Experiences.
Think of this. While someone’s playing the game on the HMD, someone else with the Spectator Screen on a Table or Desktop Display, could very well change in Real-Time an asset’s material or even the loaded level through level streaming.