Amazon.co.uk:Customer reviews: Garmin Speed sensor 2 & cadence sensor 2 - measurement and storage of speed, cadence, distance via ANT+ or Bluetooth LE. Mount on wheel hub.
Garmin Speed Sensor 2 vs Cadence Sensor 2: Which One Should You Buy? - YouTube
Garmin Speed & Cadence Sensors V2 with ANT+/Bluetooth Smart: In-Depth Review | DC Rainmaker
Garmin Bike Speed 2 and Cadence Sensor 2
Garmin Speed & Cadence Sensors V2 with ANT+/Bluetooth Smart: In-Depth Review | DC Rainmaker