Sources

Garmin, Oura, Polar, Withings, Amazfit, and hundreds of apps already write into Apple Health and Health Connect — if it syncs to your phone's health store, Faceva sees it through the phone app. No per-brand setup. And for everything else there is your personal API: any script you trust can log events — see the developers page.

Connecting a calendar or uploading an export? That lives in the Import Center — including the direct Google Calendar import and .ics upload.