Actually Sven, that is a real product. They're called Masque Wall Plates I think. Notice the warning at the bottom of the bag.... well I'm sure someone would try if that wasnt there. I dont trust them for soome reason, but I'm really not sure why...
Two thoughts from me. I remember and old inspector saying the ground should be the first to make and the last to break. If the ground prong is up the ground can disconnect before the hot and neutral. Thats why it goes down. Gravity being what it is. Second how many apliance today have grounds on them so the point of the ground protecting seem to be mute. Just my 2 cents.
Right the first time sparked! I only wish I had photoshopped the holes in. Some consumer (read sucker) will probably think these things are great and plug his space heater in one hole, and the outlet strip in the other. The shallow prong penetration is what bothered me too, and the thought of dust/debris building up between the cover and the receptacle is disturbing.
My old apartment was ½ done with those Masque things... The maintenance crews were in the process of changing the prehistoric Slater backwires out to Decora's when the Home Depot a block from there imported what I can honestly say, isn't the greatest idea... I looked behind some of them & found the original recept with the prong holes nice & gray from overheating... But hey, they "look" good... (Till they melt) I'm kinda suprised to find a UL listing on those as well, since they do inhibit full insertion into a wall recept...