I searched here but did not find this matter being discussed - probably need a better search term...

There is a product on the market, Vario Plus Sky, an electrochromatic tint film, that changes the level of tint based on the voltage applied.

Has anyone here had any experience with this material and where it is available? Their website is not really clear on that (no pun intended)... lol...

Ð*лектро тонировка Vario Plus Sky на Mercedes-Benz GL 500 (7) - YouTube