Jerry Lewis first used video assist on his film The Bellboy in 1960.
Lewis himself received a Technical Achievement Award for his invention of the video assist, a device that allowed him to view footage right after it was filmed. That way, he was able to jump back and forth between directing and acting.
Here is a more advanced system seen in the behind the scenes film “Man in Motion” shot during the making of “Three on a Couch.” The video will start at the section that shows video assist, you can go back to the beginning if you wish.
Here is a follow up post on video assist.