Stream heartbeat, breathing rate&temperature

[KPCHAN]

I am a beginner to develop app. I want to develop phone app (android & ios) to monitoring real-time data from Fitbit sense 2. I found some information from forum here. Somebody said need using companions API. But I am confused to it.

1. What is the difference between normal API and companions API?

2.How it's working?streaming data direct from smart watch to phone app develop by myself or streaming data through Fitbit phone app to app develop by myself?

3. Is the api free of charges?

4. Where can I get the SDK and API?

[Gondwana]

Start here, and follow links to guides and reference documentation.

[KPCHAN]

Before I start develop the app, may It that posibble stream the data directly from smartwatch to my own app?

[KPCHAN]

Before I start develop the app, may I know Is that posibble stream the data directly from smartwatch to my own app?

[Gondwana]

No. The watch (Device API) can only communicate directly with the corresponding companion code (Companion API), which runs within the Fitbit mobile app on the phone/tablet with which the watch syncs. The Companion API can use fetch() or WebSocket to stream data to your own app. Your app will need to function as a server. If your app doesn't run on the same device as the companion code, you may need to deal with SSL issues.

This is a VERY difficult project for a beginner.

[KPCHAN]

Thank for answer my questions.