Yes, I can comment a little bit on reaching, at certain hours...random phone calls to a household. One of the problems is that one can't always identify the person answering the phone, and in a family setting you really don't know who you're talking to if there are many people in the household. The problem seems to be the identification of the person, making sure it's that person at that time who is respecting the curfew when they're being called upon.
One way is to use voice recognition. There are other ways where we could institute some kind of biometric measurement device associated with the telephone system to make sure the person holding the set at the other end is undoubtedly the person you want to talk to. There are some ways of ensuring that the person is where they say they are.