YOU can get an iPad.... and then allow him some games on it, which he can choose with your approval.
That is what we do.
We have an iPad. It is for the FAMILY. BUT, my kids also have "their" own games on it. That way, it is more "controlled" and we are the one's that download things to it.
No way, would I actually give the iPad, to my kids to own themselves. But my kids are 5 and 9.
And we do not let our kids, take the iPad anywhere or go out with it. Unless they are with us.
And no, just because they play on the iPad, it does not mean that that is all they do. They DO do outdoor things and are very active. My kids, do not ever, get hung up on just playing video games. And they are not hooked on it. At all.
The iPad is great, and you can have a password on it too.
Even schools, use the iPad for learning.
It is VERY, useful. Even for you adults.
And, for us, we do do family things on it.
It is worth the money.
To me the solution is: get an iPad for the family, and then "give" your son some games on it... thereby, keeping your promise to him.
Many of the games are either free or costs a minimal amount. And there are fun games or educational types.
Also, you promised your son a video game. Not an operating system.
So, you can get him some games for the iPad. But he does not have to own, the iPad. Just give him some games on it.
He is 11.