I'm wearing a heart band and have just been out for a 30 minute bike ride. My heart monitor (Polar) app correctly registered the 30 minutes. The watch measured 8 minutes of excercise. The polar app measures 500 calories. The watch 308 (which is still inconsistent with 8 minutes). The polar is giving me a heart rate of approximately 92bpm and the watch 58bpm. The watch was correctly worn. I've previously worn a Microsoft Band and that is close to the Polar.