I remember seeing this folding 3-pin UK mains plug design some time ago. At the time I thought that a major flaw in the concept was that it didn’t look like it would actually be able to carry 13A of current at 240V, which is the UK power outlet rating.
This BBC News article with video describes the design process and the product which has now been realised. It appears they have produced a USB power adapter for phones etc, which of course are only rated a a few watts. This is fairly similar to the sorts of power adapters that already come with smart phones where the 3-pin part is interchangeable with other pin configurations suitable for other countries.