"Privacy Glass" has a pattern of bumps and ripples on it so that it transmits diffuse light, but people can't see an image through it of what's on the other side. This is convenient most of the time — but what if you're indoors and want to look out for a moment?

Easy solution, which I've never seen implemented: a little piece of anti-privacy material, maybe in a holder with a handle, like a classic magnifying-glass. It just needs to have an inverse pattern of bumps and ridges, valleys where hills are and vice versa, so that when properly aligned and placed next to the window it will cancel out the distortions. With cleverness in designing the original privacy pattern, the anti-privacy shape can be made to match in multiple positions and even at a distance from the main window. It's like a temporary magic peephole in a door.

(for a different system with some of the same functionality, but expensive and electronic, see Wikipedia:Smart_glass etc.) - ^z - 2011-09-08