The sword has a double-edged, which has the right function to follow scientific or modern technology, and at the same time, the wrong function to the addiction mentioned. What we must pay attention to the technical lead is the one of responsibilities to the next generation as a generation who created this technology.
In my case, I bought two tablet PCs for my children, but I did not buy smartphone yet. However, my old smartphone can be used for them but it's temporarily available for games and study under one condition.
it's agreement of installation an "App" which has the feature that 30 minutes a day is the limit of usage, based on my children promise, and the "App" automatically locked when it's over.
Parental control is required before the age at which children are able to use the techniques they have learned and to make sound judgments of their own.
The most important thing here is the parental initiative. In my case, when I get home, I put my smartphone in the closet and not bring it to the living room. However, before going to bed, only business email will be checked.
I believe that dialogue and agreement between parents and children is important for healthy use and that both sides should try to protect it. Many thanks.