I don’t know about where you live but where I live voting machines serve two purposes, generate a fully filled out valid paper ballot, and count said paper ballots. Paper is the backing “technology” regardless of the usage of voting machines, and allow for the auditing/recounting that we’re hoping to see.
This is literally already a feature on samsung’s OneUI, I use it to watch movies with the wife on airplanes and the like. Sync issues between bluetooth devices would only be a problem if you were trying to use it for like a surround system or something.