The “IGUANEYE Jungle” grabs onto your feet and lets you move freely on any type of surface. A minimal piece of technical rubber only wraps around your big toe and your heel. By doing so, it secures a thick and soft ergonomic sole that attaches to the rubber piece like a 3D puzzle.
http://www.core77.com/projects/71040/Sandals-Inspired-by-Amazonian-Tribes-Who-Dipped-their-Feet-in-Tree-Rubber-for-Protection