I have seen the mirror as well.
To be honest. As budget as it gets for hiding a screen. Curtains? Or if you could put in a cut in your wall to flush mount the tv, you could just put a painting over it and manually remove the painting if you needed to use the TV.
Yes there are motorized systems, and some very cool "tricks". But at a certain $ it sorta starts to get to the point where is it worth it.. My .02 though.