Controlling Camera iview with External Phyiscal Camera/Device? Example inside(Live Action)

I have an interest in digital makeup/Mocap…and test shooting things live… I’m having a hard time finding any information on the right terminology to shoot for. We saw at GDC with the Serkis demo, as well as the other one, that its possible to use an external device to control the view inside of UE4… what is this called in the world of UE4?

Any help would be greatly appreciated.