Yes, this is a design concept, it's called Moov, and it lets the rider change the separation between the rear wheels, enabling spectacular acrobatic stunts. Using what he calls "biomechanical muscles" to make it work, student designer Jean-Michel Raad created this concept which won first prize at the Coventry University MA Design Show. This is one bike design we'd like to see built.

Bust a Moov: concept bike goes 'biomechanical' [Sci Fi Tech]