Simple digital clockface, focusing on heart rate in large print. Yes, time (hh:mm) is also shown :-).

Details: Heart rate (largest number on screen!) can change color: normally green, red above a threshold, and yellow if threshold was previously exceeded. Threshold can be defined in the companion app; yellow resets to green through button in companion app, and every day at midnight. Below the heart rate, the time since last heart range measurement is shown. This helps to identify if there is a problem with the sensor, and/or know how long the fitbit wasn't used.

Update 2022-03-17: minor update to ensure "reset to green" really happens every time the date changes, even if the fitbit device does not call my code at exactly midnight.