This is just the first step to overlaying someone else on top of you. Soon groups of bros will assemble to watch each other simulate sex acts as hot chicks on TV.
Nothing about this really NEEDS the depth sensor to work, as long as the camera stays stationary and is reasonably low-noise, but it's still a cute use of it anyway.
Explain what is going on here... is it clipping out his shadow and making it transparent, or what? There's a few brief seconds where we see the guy standing in front of a light source from what appears to be the other side of the room.
Probably what Raggamuffin said, yeah. Most likely the depth sensor image is being passed in as a parameter to a simple refraction shader, that's being used to render a single polygon that's textured with the room image.