Earlier quoted context omitted.
> We can't demand that parents be held accountable for what their children do while also forbidding parents from knowing what their children are reading, watching, writing, hearing, or saying. There's no reason that knowledge has to be garnered surreptitiously. (If your answer is "if it's not surreptitious, then kids will try to bypass it" … well, they will anyway.)
Nobody said it had to be surreptitious. And the app we are all discussing is explicitly not surreptitious. If you go back and reread the original ask HN comment, he says that it is visible.
The comment (https://news.ycombinator.com/item?id=29571643) to which you were responding (https://news.ycombinator.com/item?id=29571750) says:
> You're asking me? Ok: it should not be possible for you to install surreptitious screen recording software on an iPhone.