The Fitbit Charge 4 is receiving its second major update. While the previous one was focused on positioning, this one (first spotted by Wareable) is all about health data as several Fitbit Sense features have been ported over. First off, the Charge 4 now shows proper readings from its SpO2 sensor on the smart band itself. You can use the new blood-oxygen watch face to keep an eye on that. Also, the band will now track your skin temperature (something only the premium Sense watch could do). Even better, Fitbit is making the Health Metrics dashboard free for Charge 4, Versa 2 and Inspire...
Source: https://www.gsmarena.com/fitbit_charge_4_update_shows_spo2_data_on_the_band_itself_tracks_skin_temperature-news-47698.php