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Vitals & Offline Monitoring

Capturing vitals even when the network is not there

Hospitals and community settings lose connectivity constantly. This explores capturing vitals offline and syncing them safely later, plus connected-device and sensor concepts: alerts, reliability, and monitoring built around the patient rather than the machine.

Tools I used

PWAService WorkerIndexedDBIoT sensorsCloudflare D1Drizzle
Chapter one

How it started

The internet drops exactly when you need to record a vital sign. So I built for the drop, not around it.

The journey

What actually happened

Offline-first sounded advanced until I saw the parts: a service worker to keep the app alive without a network, IndexedDB to hold entries on the device, and a sync routine to push them up when the signal comes back. Adding sensor readings raised the question of trust — a number from a device still needs a human to confirm it makes sense. This project taught me more about how the web actually works than any tutorial did, because every concept arrived attached to a problem I already had.

The conversation

Moments that changed the build

  • Me: "It must record with no internet." → Service worker plus IndexedDB, then sync on reconnect.
  • Me: "What happens if the same reading syncs twice?" → We designed for conflicts before they happened.
  • Me: "Show the nurse what is not yet synced." → Trust needs visible state, not silent magic.
Honest part

What broke

Early sync produced duplicate readings when connectivity flickered. Fixing it forced me to learn what a conflict strategy is.

Takeaway

What I learned

Offline is not a feature you add at the end; it is a decision you make at the beginning. And every reading needs a human sanity check.

Next

The ebook from this project

  • The Vitals & Offline Monitoring Story

    Capturing vitals even when the network is not there

    Ebook · $9.00

    Read it