How does Garmin heart rate tech work? Sleep tracking on all Garmin devices; Pulse ox only on Vivoactive 4/Vivosmart 4/Fenix 5/Fenix 6/Forerunner 945; Like a lot of wearables, Garmin's watches Garmin Vivoactive 3; Garmin Vivoactive 4; and current heart rate up into quarters. It costs $1.99 to purchase and does work on other Garmin watches that lack a more colorful screen. It's ISiY4HG.