Ok .. here is my issue. I do intervals. I cannot feel the Vivoactive HR vibration to tell me to switch between walk and run. It makes a lot of noise .. but feeling it absolutely no. Even sitting here at my desk .. I cannot feel it. It goes thru the motions, but effective .. not at all.
Maybe mine is defective .. I doubt it. I wear headphones, so hearing it is not going to happen. My Forerunner at least I can feel. Sadly it looks like I will have to use the Forerunner (a great device but syncing is a major pain with no Bluetooth).
The Vivoactive HR .. does not really vibrate, just makes noise.