Yeah, that's pretty much what I am imagining. You're right about needing some teeth - maybe the legislature could define a spec, and penalties for implementing the feature in a commercial product without actually following the spec.

I really think all we need is what you describe in your third paragraph. It doesn't need to be bulletproof, it just needs to be an easy way for parents to set the level of content their children can access without them having to hover over their children at all times. Something like that could easily be set up in the Genius store when someone gets a new iPhone, or set up at first boot on an Android phone. That's like 90% of the devices anyone is actually worried about. Windows support of the feature would take it to like 99.9%.