Biometrics API · Vexo Docs

Signal families

Every metric the API serves belongs to one of five families. Each family is a separately grantable scope, so the wearer can share heart rate without sharing sleep. Request only the families your product reads.

Name	Type	Description
hr	bpm · 1 Hz	Heart rate from the optical sensor, smoothed over 5 seconds. Requires biometrics:hr.
hrv	ms · 5 min	Heart rate variability as RMSSD and SDNN over rolling 5-minute windows. Requires biometrics:hrv.
temp	°C · 1 min	Skin temperature deviation from the wearer's rolling baseline, not absolute temperature. Requires biometrics:temp.
motion	class · 1 Hz	Activity classification (still, walk, run, cycle) plus step and cadence counters. Requires biometrics:motion.
sleep	stage · 30 s	Sleep stages (awake, light, deep, rem) with nightly summaries after wake. Requires biometrics:sleep.

Unit and on-device sample rate per family. The scope named in each row is what the wearer sees and grants.

Read a window

Query any family over a time range. Points come back typed, with a per-point confidence score, and the response is stable across SDK versions.

GET/v1/biometrics/{signal}

Read an overnight HRV window

hrv-window.ts

import { Vexo } from "@vexoring/sdk";

const vexo = new Vexo({ token: process.env.VEXO_USER_TOKEN }); // vx_user_9f2k...

const window = await vexo.biometrics.read("hrv", {
  from: "2026-07-17T22:00:00Z",
  to: "2026-07-18T06:00:00Z",
  resolution: "5m",
});

console.log(window.points.length); // 96
console.log(window.points[0]);
// {
//   ts: "2026-07-17T22:00:00Z",
//   rmssd: 61,
//   sdnn: 54,
//   confidence: 0.97
// }

Query parameters

Name	Type	Description
fromrequired	RFC 3339 timestamp	Start of the window, inclusive.
torequired	RFC 3339 timestamp	End of the window, exclusive. Windows cap at 31 days per request.
resolution	string	Point spacing: raw, 1m, 5m, 1h, or 1d. Requests below a family's native rate return the native rate.Default: 5m

For live use, subscribe to one or more families over a single websocket. Events arrive as each family's native window closes, so an hrv subscription ticks every five minutes and motion ticks every second.

Live HRV and temperature

subscribe.ts

const sub = vexo.biometrics.subscribe(["hrv", "temp"], (event) => {
  if (event.signal === "hrv" && event.rmssd < 40) {
    flagRecoveryDip(event.wearer, event.ts);
  }
  if (event.signal === "temp" && event.deviationC > 0.6) {
    flagTempDeviation(event.wearer, event.ts);
  }
});

// Revocation closes the socket with code 4403 within five seconds.
sub.on("close", ({ code }) => {
  if (code === 4403) stopProcessing();
});

Sampling and precision

The ring samples its optical and thermal sensors far faster than the API's published rates, then downsamples on-device to save battery and bound what leaves the wearer's hand. Published rates are the contract: they hold across firmware versions, and every point carries a confidence score from 0 to 1. Points below 0.8 confidence are flagged, never silently dropped.

On-device processing

Signal fusion, baseline modeling, and stage classification all run on the ring's coprocessor. The API is a read surface for derived metrics, not a pipe to the sensors.