On the wrist
A 2024 PMC review confirmed that HRV-guided training produced greater endurance improvements than fixed-schedule programming. The practical requirement: a smartwatch on your wrist throughout the full training cycle. For collectors, Smartlet removes the choice between the mechanical watch and the training data.
Global AFib prevalence rose from 33.5 million to 59 million between 2010 and 2019. Europe projects a doubling by 2060. Smartwatch ECG detection achieves 95 percent sensitivity and 97 percent specificity across 17,379 patients in 26 countries. Six documented cases show what this means in practice.
Reflectance photoplethysmography places the LED and photodiode on the same side of the skin. There is no transmission through tissue and no orientation required. The three-axis accelerometer detects gravity on all axes simultaneously and adapts to any declared configuration. Skin contact governs everything else.
The weight question about Smartlet is settled on the product page itself. With a connected device, Smartlet weighs 60 to 100 g — the same range Smartlet publishes for standard stainless steel bracelets on the market. The Apple Watch Ultra 2 weighs 61.4 g, less than any Rolex Oyster bracelet alone.