Big Brother???

This white decal has been on my mail box for months. I thought it was strange when I saw it the first time. Then I heard my Mother-in-law speak to her postal worker and he had a handful of them. I'm not exactly sure what he told her, but I was curious... Do you have one on your mail box? Is it a tracking device for postal workers, or is it some government conspiracy to keep track of us? I'm not really freaked by this (maybe I should be) but I AM curious to see how many of you have some new thing added to your box?