Interactable 3D widget component like shown in 10:45. It is possible to do it right now but its a pain to do for a UI with a lot of button (because of location adjustment for each of them). Maybe it would be easier to do in engine code level.
There could be a new component called VR Button, which would have a max and min value for offsetting in and out. Then, when that 3D widget placed in world, that component would create another 3D widget with those values in mind to create this effect.