Garmin's Edge bike-specific GPS has proved to be a popular training tool, and the 305 combines a personal trainer and cycle computer. It's both rugged and lightweight to withstand the rockiest trails while attached to the handlebars, and automatically measures your speed, distance, time, calories burned, altitude, climb and descent, and records this data for your review. For extra-precise climb and descent data, Edge 305 also incorporates a barometric altimeter to pinpoint changes in elevation.