Definitely would love this for 1 I have two young children and they both need to go on the iPad or phone for educational apps reason. I had to jailbreak so I can just us me biotouch on the iPhone 5s which I believe apple should look at and applock on the iPad.
These days there are too much sensitive stuff and also vile stuff on the net bad I have to do my best not to expose them either indirectly not doing my parent duties and protect them going on these small computers
That's another example where it would work well for you. I think it's a great feature to have for those of us who need it. Plus if they throw in how it is currently (just on/off switches) then it wouldn't require much work to add that.