Instructables user dimovi took an old LCD monitor and moved the top polarizer from the surface of the screen to a pair of glasses worn by the user. Others who look at the monitor, without the polarized glasses, see only a white rectangle. Besides the übergeek cool factor, the mod could be quite useful if you’re concerned about folks looking over your shoulder at the coffee shop.

(If you’re scratching your head right now, and could perhaps use a brief refresher on how liquid-crystal displays work, you’re unlikely to find a better one than Bill Hammack’s excellent video on the subject.)