I mentioned it; it is a very nice safety feature, we tried to use it (we were on the public beta) but it doesn't quite fit our use case, where instead we want something completely unattended, whereas Check In is more intentional, like you plan to do something ahead and set up a dead man switch that will notify people if something looks off.
Interestingly enough when one of us sent messages like "is everything alright?" the recipient got a prompt in Messages to try out the Check In feature.
Interestingly enough when one of us sent messages like "is everything alright?" the recipient got a prompt in Messages to try out the Check In feature.