https://www.youtube.com/watch?v=_d6KuiuteIA
Such an interface allows you to play virtual keyboards in mid air -
https://www.youtube.com/watch?v=sX1VG9KNyDA
Which I'm sure will be put to use on the home stereo. 8)
Also it will allow positioning of the holographic sound by waving the hands instead of using the joystick.