You need a Bluetooth 4.0 (also known as Bluetooth Smart or BTLE – Bluetooth Low Energy) receiver to log information from the sensor. The receiver may be a Bluetooth 4.0 enabled smartphone, GPS or other device.
If using a smartphone, you will also need a fitness app.
For iPhone, you need at least an iPhone 4S or above running iOS 5.0 and above. Bluetooth enabled apps available on iTunes include, BioLogic BikeBrain (with Training Module upgrade), Runtastic, Strava, and Wahoo Utility.
For Android devices, you need a phone with the Bluetooth 4.0 chip and run Android 4.2 or above, many fitness apps are available in the Google Play store.
Some Windows Phone 8 phones, such as the latest Nokia Lumia series have Bluetooth 4.0 chips, but may not have the APIs to use Bluetooth sensors.