People aren't going to make decisions just to save the earth says Chris Gay. Gay isn't flogging a solar-powered gizmo or a carbon-trading scheme. He's setting insurance. His company, MileMeter, is looking to revolutionize car insurance -- while creating incentives to drive less. Dallas-based MileMeter is the first company to offer pay-by-the-mile policies, but the idea goes back to the 1980s. After a recent retooling that allows people to buy more miles as needed and to role over unused mileage, the company is planning a national rollout in as little as a year.