With my old sensor approaching the end of its life I was lucky enough to see Nike offering free sensors to ' runners of my level '. However on its arrival I found it wouldn't work! Oh well as it was free anyway I went out and bought a new one - which also would not pick up. After exchanging it and encountering the same problem for a 3rd time I am now wondering- is there something I need to do to my I phone to connect to a different sensor? I'm still having no problem connecting to my old one?