https://www.tandfonline.com/doi/full/10.1080/21548331.2019.1656991
Abstract
Handheld medical devices and smartwatches that measure BP without a cuff have recently become available. Since these measurements are relatively more user-friendly than conventional cuff-based measurements they may aid in more frequent BP monitoring. We investigated the accuracy and precision of two popular cuff-less devices: the Everlast smartwatch and the BodiMetrics Performance Monitor.
Conclusions:
The Everlast smartwatch and the BodiMetrics Performance Monitor we tested are not accurate enough to be used as BP measurement devices.