What "offline" means for a heart rate app
Your Apple Watch sends heart-rate readings to your iPhone directly, and Apple Health stores them on the phone. An offline heart rate app reads that local data and draws its charts on the phone too. No step needs a server, so nothing breaks without the internet, and nothing is uploaded when you are online.
Why it matters
- Privacy: data that never leaves the phone cannot leak from a server.
- Reliability: works on flights, abroad and in basements.
- Speed: no loading spinner waiting for a response.
- Longevity: no server that could be shut down.
How to test any app
- Turn on airplane mode.
- Force-quit the app and reopen it.
- Check that charts, history and every screen you use still work.
If it all works, the app is doing its work on your phone.
What you give up
| Offline | Cloud |
|---|---|
| Data stays on your phone | Web dashboard in a browser |
| Works anywhere | Sync across several devices |
| No account | Server-side backup and sharing |
Your data is still backed up with your normal encrypted iPhone backup.
70 BPM works offline
70 BPM reads heart rate from Apple Health and events from your calendar, both already on your phone, and shows them together. It works in airplane mode, needs no account and does not upload your heart rate. It is free.