One time I worked at a zoom competitor, and our team got to prototype a "detect if these people are in the same room as each other" feature for dealing with echo cancellation etc, where everyone's laptop would emit a unique high frequency, and everyone's laptop would listen for other frequencies. Of course it worked in pristine conditions and fell down in the real world. But it was a fun experiment...

People need to learn manners, nobody should be using video calling without headphones. It's insane whenever someone joins and we hear all their background, feedback of whoever is speaking, etc as if nobody has ever told them to mute or stop using speaker in their life.