If you have a dedicated heart rate monitor that is constantly writing data to the Health App (such as the Apple Watch) Fit Heart will display your average heart rate during the course of a day.
Fit Heart shows you what workouts you did on a certain day, allowing you to gain insight into how exercise affects your heart rate.
Your privacy is important to us. Our app does not collect ANY personal data from your device. None. We don't even track your workflow through our app. Data synced with iCloud is stored in your private container that Apple does not allow us to read. Only you have access to your data. Your health data is stored in two locations on your device. The Health App is the first location. The other is within the Fit app itself for data the Health App doesn't store (like the number of reps you do during a lift). This data is not shared with other apps or any third parties.