Filament Labs

Apple Watch + HealthKit HRV

hrv/spark

Your HRV. Raw. Beautiful. On your wrist.

HRVSpark turns your HealthKit heart-rate variability samples into calm, glanceable watch-face sparklines. No readiness score. No stress label. No verdict between you and the signal.

Built for glanceable raw HRV

10 Complications Multiple watch-face formats.
4 Windows Short and longer-range views.
0 Stress Scores No algorithmic verdict layer.
1 Private Signal Your HealthKit data stays yours.

A window, not a verdict.

The line matters more than the label.

Heart Rate Variability can be a useful window into recovery, strain, and autonomic state. But the moment a product turns that signal into a score, color, or warning, it starts shaping how you feel before you have even looked at the data.

HRVSpark takes the quieter path. It puts the raw HRV shape where you can see it repeatedly: on the Apple Watch face you already check all day.

You bring the context. The app brings the window.

The instrument

Designed for noticing, not reacting.

HRVSpark is deliberately calm: high contrast where it helps, soft glow where it belongs, and no color-coded judgement attached to the value. The watch face becomes a small instrument panel instead of a daily report card.

HRVSpark displayed on an Apple Watch Ultra-style case with raw HRV complications.
Glance A small sparkline shows the shape, while the large number keeps the latest value readable.
Tone Neutral presentation reduces the urge to chase a colored score or outsource intuition to someone else's algorithm.
Place The complication lives beside the time, date, and activity data: available when you want it, quiet when you do not.

HealthKit in view

Four windows, one honest source.

8H

Short-range shape

Recent HRV readings stay close to the surface, useful for spotting the shape of a day as it develops.

24H

Daily texture

A full-day window helps separate single readings from the broader rhythm of sleep, work, movement, recovery, and intervention.

7D

Weekly baseline

The seven-day view makes repeated patterns easier to notice without turning them into a score.

30D

Longer arc

A month of raw values gives context for drift, recovery phases, and the conditions that move your numbers.

Design philosophy

Raw means the app stops trying to be the authority.

"I wanted to see the actual shape of what was happening, not a number summarizing it. The crash after hot yoga. The rise after cold exposure. The drift during sleep. That shape was more useful than a verdict."

- the creator

Analysis appsReadiness score

HRVSparkRaw SDNN value

Analysis appsColor-coded verdict

HRVSparkNeutral sparkline

Analysis appsProprietary interpretation

HRVSparkHealthKit data in view

Analysis appsTell you what to do

HRVSparkShow you what happened

Who it is for

People who already bring context.

The self-experimenter

You are already tracking sleep, recovery, breathwork, training, cold exposure, or stress. You want a cleaner window into the signal.

The HRV veteran

You may use deeper analysis tools, but you still want one watch-face view that simply shows the raw data.

The anxiety-conscious

You do not need a product telling you whether today is good or bad before your feet hit the floor.

The data-over-decoration type

You care about the shape and the value. Everything else should earn its place.

Simple pricing

Try it free. Unlock once.

Free to download and try. $2.99 one-time unlock for Pro. No subscriptions, no accounts.