On the watch's bottom, there's a small optical heart rate sensor sitting in the middle. (techradar.com)
The wearable is the company's most advanced yet, offering standard fitness and sleep tracking, along with optical heart rate monitoring, GPS, and standalone music functionality. (pocket-lint.com)
It has all the usual activity and sleep tracking features, along with optical heart rate monitoring, built - in GPS and standalone music functionality. (pocket-lint.com)