What would be far more helpful is to just turn off screens that the person hasn't interacted with. I've been on too many late night flights where the screens for empty seats, or for people who are staring at their iPad have made it really hard to sleep(eye masks are uncomfortable for me). I've even seen people actively trying to sleep with the full brightness screen right in front of them because it's not obvious at all how to turn them off(usually you have to find the brightness menu and press the down button a dozen times).