Min-Kyu Choi, a graduate of London's Royal College of Art, is rethinking that part of the world's bulky Type G three-pronged plug (similar to what you see here in the United States,
but at a different voltage but with a few key differences). The Folding Plug is the result of that, which can be used either in its flat state or in a more conventional unfolded mode that still sits in the wall with a lower profile than usual.
The real beauty of the flat plug design is when you combine it with a Multi Flat Plug adapter (pictured below, middle). That lets you share one outlet with three plugs folded flat, and they don't take up all that much space at all. There also a USB adapter that plugs into the Multi Flat Plug and takes up two spots (pictured below, last).
It's a shame it's just for Europe (not to mention it's only a concept), but the ol' plug-and-outlet combo is something I wouldn't mind seeing cleverly redesigned.