I feel it is super important for parents to be aware of what their kids are doing online. Even spaces designed for children have security issues as well as threats that purposely target children. I want to use this thread to compile useful tools, services, and tips to help parents better understand their security options to protect their children online.
One app that I know of that my brother uses is Kaspersky Safe Kids. It compliments other security apps and services very well and adds another layer of security for people that have children and teens. It comes with real time alerts, GPS tracking, YouTube safety searches, screen management and more.
I am not very familiar with parental options these days but I believe there was once an entire system that was called K9 to protect kids. I don't know if they are still around. I know Linux has options that are kid friendly as well. The entire system is built around being safe for kids.