hrv/spark
Your HRV. Raw. Beautiful. On your wrist.
Data without the verdict.
A window, not a verdict.
HRVSpark puts your Heart Rate Variability data exactly where you want it — on your Apple Watch face, as a live sparkline graph, always visible, never interpreted.
No readiness scores. No stress labels. No algorithm telling you how to feel about your own physiology. Just your raw SDNN values, beautifully displayed across four time windows.
You already know what a cold plunge does to your HRV. You already know what poor sleep looks like in the numbers. HRVSpark gives you the clearest possible view of your data — and trusts you to know what it means.
The Problem With HRV Apps
Heart Rate Variability is one of the most revealing windows into your autonomic nervous system — a daily snapshot of how recovered, stressed, or activated you are at a physiological level.
And yet most HRV apps take that raw, honest signal and bury it under a layer of interpretation. You get a score. A label. A color. A verdict.
Your readiness is 62. You are moderately stressed. Recovery recommended.
For the curious, the self-directed, the ones who already know their own bodies well enough to find those verdicts condescending — it produces exactly the opposite of the intended effect. Seeing a low readiness score first thing in the morning is its own stressor.
Design Philosophy
"I always drift up and vary a lot while sleeping. The numbers always crash after hot yoga. They go up with tvTENS on my ear. They go WAY up with a cold shower or ice plunge. I wanted to be able to see THAT — not a score or a color behind an opaque interpretation layer."
— the creator
No interpretation means no color-coding by value. No anxiety means subtle aesthetics — dark backgrounds, soft blue glows, data that whispers rather than shouts.
Complication-first design means it's always there — not something you open, but something you glance at. Part of your watch face like the time and the date.
"The no-scores approach makes total sense. I found myself chasing the number instead of actually understanding my patterns. Removing the interpretation layer and just looking at the raw 7-day trend changed how I used the data completely. The anxiety that comes from a colored score or verdict is real. Raw numbers let you build your own intuition over time instead of outsourcing it to someone else's algorithm."
— beta tester
Who It's For
You're already tracking. You've already noticed patterns. You don't need an app to tell you what your body is doing — you need a better window to see it.
You do cold exposure, breathwork, vagal nerve stimulation, HRV-guided training. You need granular, honest data to evaluate your interventions.
You've used the other apps. You liked some features. But you got tired of the interpretation layer — the gamification of your own physiology.
When the app stops telling you you're stressed, checking your HRV stops being a source of dread. It becomes simply informative.
What Makes This Different
| Other HRV Apps | hrv/spark |
|---|---|
| Readiness score | Raw SDNN value |
| Color-coded verdict | Neutral sparkline |
| Proprietary algorithm | Apple HealthKit data |
| Opens an app | Always on your watch face |
| Smooth the data | Show the data |
| Tell you what to do | Show you what happened |
Coming Soon to the App Store
Currently in TestFlight beta.
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