I don't think the cheap light sensor would have a fast enough polling rate for that. And if you increase the polling rate I will just put a phosphorescent sticker that absorbs and reflects the light coming out of the led with a good enough afterglow that the photoresistor will still pick up as some value and still allow for recording.

Also what is the implication here? If you cover the hole accidentally for one microsecond do you invalidate the whole recording? Does it need to be covered for more than one second, two seconds, ten?

All of that for what? So that in 2 years we can have chinese off-brand clones for 50 dollars that offer no security mechanisms anyways?

We all need to understand this is the new normal, being able to be recorded anywhere anytime. Just like you can get punched in the street anywhere anytime. We only act on things that can be proven to have caused you prejudice in court.