I think you're being a bit hyperbolic if you say that locking someones cell phone is the same as putting them on the leash.

You make a few valid points there, but in essence I think we disagree on the severity of punishments.

I'd say being grounded is far worse than having your phone locked, yet you'd call it a fair punishment that should come first.

I'd also say that a cellular phone isn't essential to life, like food is. While you might see many middle/upper class children with phones, they're still a luxury item.