💙 Web Bluetooth navigator.bluetooth — zero libraries

The browser can talk to Bluetooth Low Energy devices directly. This page connects to any standard heart-rate monitor — a chest strap, many fitness watches in broadcast mode — and streams your pulse, live, into a web page.

💓 Connect a heart-rate monitor

Chromium-only for now (Chrome, Edge). The permission chooser lists nearby devices — the page never sees anything you don't pick.