I think the way it has to be brought in is through the fourth official watching the game with quick replays - let the ref make the decisions and then the foutrth official does a quick check if the ref is BLATENTLY wrong then he lets him know and it's overturned.
Will make being at the game interesting as - PEN is given, supporters go wild, 10 secs later it's overturned and attacker gets yellow card, other supportersgo wild and take the mick.
I expect within a short time a lot of the diving would also stop in the box as the players would know whats coming.
Also if there is a off the ball incident then if 4th official seen it - lets ref know game stopped and player sent off immediately or booked at next normal break.
I don't see many down side to video technology