Was it not DC Raimaker who managed to sell the Polar OH1 even to scientists?
https://www.dcrainmaker.com/2019/03/polar-oh1-plus-optical-hr-sensor-in-depth-review.html
Even scientists became interested in the Polar OH1, and tested the HRM with a 50 000 USD g.tec medical multi-purpose device:
and wrote a paper with it:
Validation of Polar OH1 optical heart rate sensor for moderate and high intensity physical activities
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217288
But then Polar made a firmware update of the Polar OH1:
And did as a consequence not many scientists loose their interst in OHRMs? And only 52 seem to be still interested in it: