These flipflops have got an arch-support with a hidden pocket where you can leave your keys and wallet while you're in the water. I have no idea whether the rubber is stiff enough to make walking on your car-keys comfortable, though.
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.