Most phones these days can be put on to vibrate and that can allow the recipient to leave the room before answering. I'd take a guess that most of those who need to be in constant contact would know that and, out of simple courtesy, would do that.

It's very easy to forget to turn off the phone in these situations but most of those who do forget would, I am sure, turn it off or leave the room hastily if the phone erupted.

For the a*******s who won't - embarrass the hell out of them! More entertainment for everyone else. :0)