BioLogic Bluetooth Smart Speed/Cadence Sensor Measure your speed and cadence, all from one compact device Bluetooth (4.0) Smart  get real-time data wirelessly, no dongles required Works with Bluetooth Smart Ready devices, including iPhone 4 or later and Android smartphones running Android 4.3 Energy-efficient  approximately 700 hours of use from one battery Works with many cycling apps, including BioLogic BikeBrain for iPhone.