How to Spot Your Boss is Coming?

The mirror for your computer screen. Imagine you are at work, watching the posts on Damn Cool Pics or playing some game on your pc. Suddenly, your angry boss comes behind you and sees what you’re doing. Well, you can imagine what happens next.
So, to avoid this, you install this mirror on your computer screen and you can always see when your boss is coming, then, you open Word and continue "working".