Paired with the fenix - what's the use of the pro over the HRM run? The strap itself doesn't do anything that the watch doesn't do. You can't start a workout without a watch so the HR strap can't be used on its own. I tried taking the watch off once and using the strap and it didn't record heart rate whilst it was out of range of the watch. I think that was maybe a glitch but I'll try it again. Can the strap be used for all day heart rate tracking and body battery for a manual worker? I'm trying to work out the reason people spend the extra £ on this but I'm struggling. I expected to be able to use it without a watch, but nadda.