In "Fahrenheit 451," Ray Bradbury described a futuristic radio that could be worn inside the ear. It would be "a hidden wasp snug in its special pink warm nest," he wrote, and the conduit for "an electronic ocean of sound, of music and talk and music and talk, coming in on the shore of [your] unsleeping mind." That was more than 50 years ago, but it's not a bad description of iPod headphones.