Going on the basis that we model manners to our children I am struggling with how to treat mobile phones: they are constantly on alerting us to phone calls, messages and emails... and more and more now. If we are in the midst of a conversation or a game, do I pick up if it rings? (signalling that the person at the other end is more important than the person, even the Little Person I am talking to there and then) Do I look when it beeps? What do you do?
We don't answer phones if we're at the table or during story time. If I'm in the middle of a game, I ask if it's ok with the kids before I get the phone. My mobile never rings anyway, it's usually out of charge or out of earshot ( or both ! ).
If it is going to annoy you (in the future) that they answer the phone when you're talking to them, then don't do it yourself. Don't even look at it. Otherwise you have no basis for complaint down the line!