Kacbu lists 33 Smartwatches that stand out for Health Tracking: Apple, Fitbit, Samsung +4. Each product is here because its editorial assessment found it strong for this use; the order is the Match score, computed from official specs and verified editorial tags, with the reasons under every card.
For health tracking, having a sensor and a feature working are not the same thing. A measurement may exist in the hardware but be off in the software, or only enabled in some countries; features like ECG and blood pressure need approval country by country. Look at the page where the maker states which feature is active where, not at the sensor list.
Each card carries what sets the product apart. Open the product page for its strengths, weaknesses and alternatives.

42 mm · Up to 24 h · Yes

46 mm · Up to 24 h · Yes

40.5 mm · up to 144 hours · Yes

47 mm · up to 60 hours · Yes

47 mm · up to 60 hours · Yes

40 mm · up to 40 hours · Yes

44 mm · up to 40 hours · Yes

46 mm · up to 30 hours · Yes

40 mm · up to 30 hours · Yes

44 mm · up to 30 hours · Yes
41 mm · up to 30 hours · Yes
45 mm · up to 40 hours · Yes
41 mm · up to 30 hours · Yes
45 mm · up to 40 hours · Yes

48 mm · up to 144 hours

44.5 mm · up to 96 hours · 5 ATM

44.5 mm · up to 96 hours · 5 ATM

45.6 mm · up to 168 hours · 5 ATM

43.5 mm · up to 168 hours · 5 ATM

48.5 mm · up to 72 hours · 20 ATM

40.5 mm · up to 144 hours · 50m

41.2 mm · up to 96 hours · 5 ATM

47.5 mm · up to 576 hours · 5 ATM

49.1 mm · up to 432 hours · 5 ATM

48.1 mm · up to 432 hours

up to 288 hours · 5 ATM

47 mm · up to 360 hours · 5 ATM

47.3 mm · up to 360 hours · 5 ATM

40 mm · up to 18 hours · 50m

44 mm · up to 18 hours · 50m

42.9 mm · up to 96 hours · 5 ATM

43 mm · up to 96 hours · 5 ATM