Blindfold or Close the Curtains

Is there a method which allows the GM the ability to prevent selected players from seeing what is currently happening on the map? In essence "hey cover your eyes while I do something" or "your character is unconscious for this round so you don't see any of this" granted I understand this kinda falls into player etiquette and meta-gaming but I believe this could really be used to great effect for numerous things. Maybe this is leaning towards an individual player fog of war, which again would enable a lot of simulated effects.