Dutch kinetic sculptor Theo Jansen creates intricate sculptures/creatures out of PVC pipes.  These creatures he lets loose on the beach and they walk by themselves powered by wind and their own momentum. Eventually he wants them to live and roam on their own in herds on the beach.  Their movement will pick up and shuffle sand in order to help preserve beaches and coastlines.  Check out this video about Theo Jansen and his amazing creations.  

http://www.youtube.com/watch?v=pCtA5kX-Ktg&feature=related