I think the concept is similar to the "3D" stickers we played with as a child.... wherein you can see 2 or 3 images as you view it from different angles. They're definitely not new, but applied to street ads with a specific purpose, now that's innovative.

This can also be used to hide/censor ads of vices and pictures of half-naked women from the point of view of children. Of course, this only works when the ads are on street level.