Here is a smart sensor that combines with your smartphone to track your indoor and outdoor cycling workouts. The SunnyFit CB100 Smart Cadence & Speed Sensor comes with Bluetooth and ANT+ connectivity. It shows your real-time data on your phone. You can use the companion app to try over 100 workouts and tour the world with real workout maps.
The SunnyFit app is available for iOS and Android devices. This sensor has a compact design and can be installed with a rubberized mat and bands. More info is available here.