This should be possible with the phone if they will make the HoloLens Miracast enabled. I don't see why it won't be. Now that would be totally awesome! No more bulk of a monitor on your desktop! If you want to go from a 22" Display to an 80" display on the wall, no problem, just snap it to the wall and expand it. I really like the idea of that.
A virtual monitor to watch a movie on, while I play a game on another virtual monitor, while a render is on-going on a 3rd, watching folding at home on a 4th, and skype call on yet another. Wait, now I can't see where I'm going with all the monitors in the way!