Please check our integration table table – only devices with a heart icon will measure heart rate with Sleep as Android. Other smartwatches with HR sensor need to go around SaA – save HR to S Health or Google Fit, from where Sleep as Android will download it. Please note that Sleep as Android downloads the measurements usually with a day’s delay (the sync is triggered once another record is saved).
This is a companion discussion topic for the original entry at https://docs.sleep.urbandroid.org//faqs/no_hr_wearable.html