I knew that a chest strap was going to be more accurate than any watch based tracker, but I was not aware that a Coospo H808S chest strap heart rate monitor (quite a bit cheaper than the Polar H10 chest strap I’m using) can also connect to various third-party fitness apps like Polar, Wahoo, Endomondo, UA Run, Garmin, Peloton and more (seemingly via its own CoospoRide app).
This chest strap does basically what the H10 does, and is also waterproof, and has Wireless HRM Dual Mode Connection like the H10.
I’m very happy with the Polar H10, but I’m due to replace the strap soon, and they are not exactly cheap (in South Africa anyway). For me, it looks the Polar strap will need replacing every 14 or 15 months.
See https://lifehacker.com/why-a-chest-strap-in-the-best-way-to-track-heart-rate-while-exercising