Whether you are preparing for that Century race, or even if you are just trying to get more fit and motivate yourself to go a little bit farther or a little bit faster every day, you will really like the addition of a speed cadence sensor with your GPS device. For ultimate fitness progress you can monitor your pedaling cadence as you ride with a self-calibrating, wireless speed/cadence sensor. It will help you track your speed, distance and pace so that you can monitor your workout performance. It measures and reports your pedaling strokes per minute, providing feedback for optimal efficiency. The Garmin speed/cadence sensor (GSC 10) is compatible with the Edge 305 and Forerunner 305. The best part is that you can use the speed cadence sensor, even on your stationary bike, so you can continue to work out even on the bad weather days we seem to be getting more of this time of year.