Fitbit has started distributing ECG functionality to the Charge 5, an advertised feature since the device's launch in August. The company has enabled its Daily Readiness Score for Fitbit Premium subscribers, too.
https://www.notebookcheck.net/The-Fitbit-Charge-receives-ECG-functionality-with-an-update-as-Daily-Readiness-Score-rolls-out-to-Fitbit-Premium-subscribers.578140.0.html