Although these particular "22" plugs from Bocci are custom made to be recessed into drywall for a shockingly classy presentation of the standard power outlet, there's little reason someone with some dry wall skills and a good eye couldn't do something similar with a standard housing. The perfectly round plugs help quite a bit, of course.
God forbid you ever need to rewire, though.
Bocci 22: The Outlet for Minimalists [Unplggd.com]
Update: Core77 has a nice video showing how it's all made.