This application runs purely on your device and does not send any data to the cloud. Any historical data is stored locally on your device that you can export as csv (comma-separated-values) if needed.
If you have a BLE enabled heart rate monitor, you can connect to it using the button below and start monitoring your heart rate. e.g. Magene H303
This app can also be installed as a Progressive Web App (PWA) on supported platforms. You can install it on your phone and keep it running in the background while you exercise.