4. Thy children shalt answer all cell phone calls from you
One nice thing about technology is being able to reach your kids at a moment’s notice. Unless, of course, they don’t answer the phone. That’s not really an option. Receiving phone calls from you, even stupid ones, is the price of admission for your kids having what amounts to a supercomputer when you were a child, in the palm of their hands. Be clear with your kids that their phones are a privilege, not a right, and if they’re not going to use them for their primary purpose (keeping the family in sync), you can take back what you pay for.
...don’t be a jerk about it, though. If the kid didn’t answer because they were running around playing instead of staring at a screen, that’s the desirable state of things.