This.
Not this.
Exactly.
At a young age, most kids wouldn't know how to use a computer for things that are inappropriate. But by the time they are 10 or 11, they'll learn, from friends with permissive parents, if not some other way. No TV in bedrooms either; kids or adults. Bedrooms are for sleeping in. Seriously, medical folks will tell you this as well, especially those who treat people for insomnia.
I know that's a radical opinion, but mark it down; if you put a computer or TV in a kid's bedroom, there will be problems. Keep those things out in the open and interact with the kid while using them, and even one step further, leave them off sometimes!
My kids got computers of their own when they went to college. Until then, there was a family computer, in the Living Room. The TV was downstairs in the Family Room. Oh, and we ate dinner together as a family 7 nights a week. One kid got his first cell phone when he moved into a boarding house without a land line his sophomore year, the other one when he graduated. Until then, they didn't need one, and never asked to have one.