Beaded Curtain Doors are great for that Greg Brady vibe, but there's a big problem: they don't keep people out! My old roommates and I once tried to use them as barriers when we couldn't afford Shoji screens (I know they're cheap, we was poor poor poor) and you know what happened? Malevolent Harpy (not her real name) would come up to the screen, and having nothing to bang her claws against would sing out, "knock knock, knock knock". I guess you had to be there but it was pure evil in vocal form.
The $2000 Watur water door, designed by Daniel Harper, is standard door width, but a continuous curtain of water streams down until you grant access and turn it off. Maybe the Watur wouldn't have stopped my roommate from singing, but at least if she'd actually attempted to step through she would have melted. You can watch the un-knocker through the water as they wait and wait and wait.
Order yours from Elsewhere.