Is it possible yet to control the output that’s normally mirrored to the monitor?
Id like a split between the normal player view and another in world camera but im not sure how to go about it. 
Is this just not possible with ue4 then?
Devs working with unity have had this stuff for sometime now.
What they are doing is tying a real world camera and then parenting an xtra vive controller to a virtual camera so the cameras viewpoints match each other. Then they record a render of only the background objects (behind the vive) and foreground objects (in front of the vive). I dont see why it wouldnt be possible but it seems likes its a C++ integration but Im not sure.
Also a user already started a Mixed Reality thread on the VR forum, we should probably keep posting on one thread so hopefully enough people see it and we get some insight from Epic themselves.