If you have an Android Watch that runs on WearOS, then you need to download this app: https://play.google.com/store/apps/details?id=de.locxserv.hyperatewearos&hl=en&gl=US
The Android App is only able to connect to arm bands, chest belts and wristbands.
You can find all compatible devices here: https://www.hyperate.io/supported-devices