With the help of the Bluetooth Smart running sensor, technology and performance while running can be improved. The sensor measures speed, distance, cadence, and stride length during training on a treadmill or in the field. The running sensor is compatible with many leading training apps, such as the Polar Beat app. The Running Index feature indicates how running performance changes. The sensor can be securely attached to the shoe and is shock and water-resistant. The sensor can be connected via Bluetooth Smart to the iPhone 4S and newer.