A couple nights ago myself and two other friends started our movies at about the same time. I was able to send them screenshots of Tautulli so we could sync within a minute or two.
I thought this would be a cool feature for the Plex or Plex Pass operator. Some sort of a movie night sync mode. We could invite users we share with into a room. Then we can play/pause the movie for everyone. It was pretty fun as we were able to hang out at our homes and enjoy the movie together, we also communicated by texting in a group chat. A friend mentioned the text feed popping up on the screen, that would be pretty cool too as a toggle on/off feature.