Exactly, any design for this stuff requires parental-involvement because every approach without it is either (A) uselessly-weak or (B) creepy-Orwellian.

If we assume parents are involved enough to "buy the thingy that advertises a parental lock", then a whole bunch of less-dumb options become available... And more of the costs of the system will be borne by the people (or at least groups) that are utilizing it.