Barometer

Air pressure and relative altitude from the device barometer

One.Barometer reports air pressure on iOS and Android, with live updates. It has isAvailable(), setUpdateInterval(intervalMs), and addListener(fn).

import { One } from 'one'

if (One.Barometer.isAvailable()) {
  One.Barometer.setUpdateInterval(1000)
  const subscription = One.Barometer.addListener(({ pressure, relativeAltitude }) => {
    console.log(pressure, relativeAltitude)
  })
  // later: subscription.remove()
}

isAvailable() is synchronous. Each event is { pressure, relativeAltitude, timestamp }: pressure in hectopascals (hPa), relativeAltitude in meters above the first reading on iOS only, and timestamp in seconds since boot on both platforms. setUpdateInterval paces delivery on Android; on iOS the altimeter delivers at its own rate and the call is accepted and ignored.

On iOS, physical devices need the motion usage description before the altimeter delivers; set native.app.pedometer.usage (see Pedometer). On web, browsers expose no barometer API, so the sensor reads unavailable and listeners never fire.