Thrumline: Heart Rate Monitor

Your heart rate, live, from the strap you already own. Thrumline connects to a Bluetooth heart rate strap or armband and shows the reading on a dial marked with your own training zones, so a glance tells you which band you are in. Record a session and it is kept: its graph, its time in each zone, and files for your training log. WHAT IT SHOWS • A dial in your own zones, with a heart that beats at your rate. • A line of the last minute, five, fifteen or sixty, coloured by the zone of each reading. • Time in each zone, as one bar. • Calories (the strap's own figure where it reports one, otherwise an estimate from your rate, age and weight), heart rate variability (RMSSD), beat evenness, and recovery from the recent peak. • What the strap says about itself: skin contact, where it is worn, its battery. • A line in plain words about the reading: encouraging when you are working well, curious when your rate lifts while you sit, practical when the strap loses contact. SESSIONS Tap Record, or let a session start by itself when the strap connects. Each one keeps its graph, low, average and peak, and time in each zone, and shares as CSV for a spreadsheet or TCX for a training log. ON THE LOCK SCREEN While you record, the rate, its zone and the time sit on the Lock Screen and in the Dynamic Island, and the strap keeps reading with the phone locked. APPLE HEALTH, IF YOU WANT IT Switch it on and each recorded session is saved to Apple Health as a workout with its heart rate. Thrumline writes only; it reads nothing from Health. ALERTS A sound, a buzz or a notification when a recording drifts out of your target zone, or when your rate stays above a level you choose. SHORTCUTS Get the current heart rate or zone, start or stop a recording, from Shortcuts and automations. WHICH SENSORS Any strap or armband that uses the standard Bluetooth Heart Rate Service, which is nearly all of them. No allowlist, no per-device support: if it speaks the standard profile, it works. Apple Watch does not broadcast that profile, so it is not supported. NO SENSOR YET? Tap "See how it looks" and the app runs on a worked example, clearly labelled the whole time, so you can see what it does before buying a strap. ALSO ON MAC The same app in the Mac menu bar, included with one purchase. PRIVACY No network access at all, no account, no analytics. Settings and the sessions you record stay on your device. THIRTY-FOUR LANGUAGES The whole interface, including every note it can show you. NOT A MEDICAL DEVICE Thrumline displays what a fitness sensor reports. It is not a medical device, it makes no diagnosis, and nothing it shows should be used to diagnose or treat any condition. Training zones are the ordinary percent-of-maximum bands used by every fitness tracker.