alright so i was on the phone and i decided to use my mb. i tried to flip up the screen with only one hand without holding it down. when i did that the mb flipped open but also flew off the back of my desk (3 feet) it was on sleep btw.. a sense of panic came over me but i saw the gray screen with the apple logo so i guess that sensor really works... after when i started using it, everything was fine... nice to know that it would be safe from a fall of a short distance..