The Wahoo Blue SC features a Bluetooth Smart (4.0) cycling speed/cadence sensor made for the iPhone 4S and 5. This sensor and App combination transforms your iPhone into a powerful cycling computer. The Wahoo Blue SC connects wirelessly to the iPhone 4S/5 and tracks your cycling speed, cadence, and distance through the free Wahoo Fitness App. Additionally, it works with other popular Apps including Cyclemeter and Strava. The Wahoo Blue SC's odometer functionality tracks the lifetime distance of your bicycle and stores the data in the device. Whether you ride with or without your iPhone, as long as you have your Blue SC you will always know the total mileage of your bike. Using the free Wahoo Fitness Odometer App, you can sync all your data once in range of your iPhone 4S, 5 or new iPad and see the the lifetime mileage of your bike by week, month and year. Wahoo Blue SC will NOT work with the iPhone 3G, 3GS, 4, or earlier generation iPads.