I see tihngs like that becoming common place.  I think (and am suprised we haven't already seen many) HDMI docks for phones that do what that video does.  I know one exists for Note 4.  It's like $40 bucks.  I may get one.
But essentially, dock your phone to a device that has USB support for keyboard & mouse, and an HDMI connection, and BAM!  instant computer.
I've done it a few times with my tablet and a bluetooth keyboard.  It's kinda neat, but not quite as useful without a trackball.