Here's the ultimate example of someone who values his privacy for watching... um... videos on his PC. YouTube user brusspup shows how to make a DIY monitor that only you can see through special glasses.
What you will need is a standard LCD monitor, a sheet of polarising filter, 3D glasses and some craft tools. Open up the monitor and strip out the polarising filter on the screen. This process requires a little care not to damage your screen while you're at it.
Then, pop out the 3D filters from your glasses and trace the size of your spectacles onto the polarising filter. Cut it and fix the polarising filters into your glasses.
There you go! Your monitor will now show a white screen to anyone, unless you look at it through the special glasses you just created.
Amazing Secret Monitor! (How To) [brusspup]