Simply place the Nike+ Sensor under the sockliner of your left Nike+ ready shoe and start running to sync it with your Nike+ Sport Watch GPS, iPhone 3GS or other Nike+ tracking device. Measures your pace, distance, time elapsed and calories burned. Not compatible with iphone 6 and 6 plus.
https://www.amazon.com/Nike-Stand-Alone-Sensor-Kit/dp/B001L6LJJS

