I was wondering if anyone else has been able to calibrate a run with their iphone 4. Even since iso 4 i seem to not be able to. It used to be that there was an option to choose wether or not i wanted to do a calibration or just a work out, but now it says i have to complete a work out then hit the calibrate button.. I complete a work out and there is no calibrate button . I mapped out my run distance with google and the sensor is about .22 miles off this is bad since i'm training for a marathon and my recent 12 miles runs have probably been 14.4 miles sigh. Please help.