It's harder and harder to raise kids in this day of age without influences from smart phones / tablet / notebook. Let me share how I overcome the barrier to advise my children how to proper use these devices, and not be controlled by them.

I installed an application on my phone to control my 3 year old from using the phone or tablet for excessive long time than permitted.

I used an Android app called "Take a Rest for Parents" from Google Play. I think they are making for iPhone but not yet released.