A while back we had phone safety lessons. I unplugged a phone (so not to make a real call) then we practised phoning 911. We then talked about appropriate times to call 911.
Another day I took one of our children on a bike ride to a payphone, then she phoned home to talk to Dad. These days everyone seams to have a cell phone, but using a payphone is still a basic life skill, I feel everyone should have. We also talked about how you don't need money to call 911 from a payphone.
Very young children have been known to call 911, saving the lives of parents, siblings and others.