Ted Selker, a research scientist and professor at MIT's Media Lab, wears the Smart Helmet he invented five years ago. What can it do? It can play music or audio books, with hook-ups for an iPod or tape cassette. It can record speech through built-in microphones and GPS, warning the wearer of a hazard on a given route the next time around. It can also detect important sounds like a fire siren to mute music when necessary. It has a Motorola cell phone with Bluetooth installed so a bicyclist can talk on the phone, hands-free, while commuting.