I use the Nike+ app with Nike Air Agitate. I have never had a problem with the app before. Two days ago, it told me my sensor's battery was dying. Today, I replaced the sensor, ran 7 miles, calibrated the app, and tried to upload. It generates the error message "Cannot sync to Nike+ Nike+ipod cannot sync workouts because Nike service is unavailable." I have tried using wifi at the gym, wifi at home, and cellular service where there were no less than 4 bars.