Polar CS Series Cadence Sensor by Polar. $24.66. Amazon.com Product Description      The perfect accessory for cycling enthusiasts, the Polar CS Series cadence  sensor lets you monitor your pedal cadence while on the road. Then, once you&#x27;ve  completed your workout, you can download your cadence graph to one of Polar&#x27;s CS  Series cycling computers for further analysis. The data, which includes heart rate and  speed graphs, helps you make the most of your high-spin workouts. The ca...