At $5,000 a pop, Segway Human Transporters aren't a fixture on Main Street just yet, but some niche markets have begun to emerge. MedExpress Ambulance Service in Louisiana puts medics on Segways so they can navigate traffic. Retailers deploy them for promotions -- staffers cruise among shoppers providing free samples. And there are rental shops. At Seaway Rentals, near San Diego, Craig Lucero charges $20 per 45-minute ride. The business will last a few years, he figures, while the Segway is still a novelty. After that, he hopes to become a dealer. "The ground floor of a promising venture -- it's very exciting," he says.