OK, after you lock the door the walls turn opaque. But, still ...
Sounds like one of the trials from the show Endurance ...
So much room for abuse to include picture taking. One little slip and it's "Smile! Your on Candid Camera!".
Auto-dimming needs to be automated or face public scrutiny.
From a distance, looks like such an easy physical hack with a piece of gum or other non-conductive material. Add to that good old brute force and your "opaque" anything can be reduced to an inert working condition, i.e. loss of electricity or other loss of functionality.
This is a solution looking for a problem.