My out of state sister - she had all the important contact info (dr, all our numbers, and our schedule - we added her to the family google calendar). She's not there in person but could find us, or give important info to the school.
A neighbor - I work from home and so does she - if I don't answer my phone she can look in the driveway and come find me if I'm not near my phone. I asked her if she minded before I did this and she said she didn't, and also offered to pick up DC in a pinch.
A co-worker of my husbands - she could find him if he was in the office and not answering the phone or know where he was if he was out of the office, and also provided the # for the receptionist - they could page DH if necessary.