Hello Olga,
Thanks for the information on Gryphon, I took a look and it is similar to Circle. However, Circle offers an application that can be installed on your kids’ phones so you can extend parental controls from not only your home network but even their mobile data network as well. This way you are always in control of what content your kids can see, as well as a few more neat features, Filter, Time Limits, Focus Time, Usage, Pause, Rewards, History, Bedtime, Location. Tap or click here for more information.