Video shows 4 sensors.. 2 of them are "pulsing" and Apple says it is for heart rate. Just those 2 or all 4? If only 2, what are the other 2 for? If all 4, why 4? If 2, why not tell us about the other 2? Etc, etc, etc.. where are all the other sensors? If for HRM only, this is a let down. Man, and $350? I'd like to have it, but no way would I pay that much. I've been looking at Suunto for a long time, but don't want to pay that price... I gotta wonder if Apple will really sell as many as they would like...