iArmBands Shoe Sensor Case for Nike + iPod Sport Kit for iPod nano / touch / itouch (Black)
I really like the the armband carrier.  Stays securely   fastened on the shoe when you run it through your shoe laces twice.  The only draw back is that it's off a little with tracking your pace.  It doesn't track as well as when the sensor is      embedded in the sole of a shoe.  Overall it's a good product.