Only watches that can broadcast your heart rate over ANT+  is currently supported by Fitillion.  If your watch supports ANT+, please check: https://studios.fitillion.com/heart-faq-studio/options/wristband/

Unfortunately, many sports watches and wrist bands currently don’t support ANT+ broadcasting, including most watches from Fitbit, Samsung, Polar, Suunto. Note that WearOS watches support is coming soon.