Filament Labs

Apple Watch + resting heart rate

rhr/spark

Your Resting Heart Rate. Raw. Beautiful. On your wrist.

RHRSpark puts resting heart-rate trends on your Apple Watch face without hiding the source. Short windows use sedentary HealthKit samples. Longer windows show Apple's daily RHR directly.

Built for transparent resting heart-rate trends

10 Complications Multiple watch-face formats.
4 Windows Short and longer-range views.
2 Sources Sedentary HR plus Apple daily RHR.
0 Hidden Algorithms No private reinterpretation.

Data without the guesswork.

Resting heart rate should say where it came from.

Most health apps present resting heart rate as a single number. Useful, maybe, but usually opaque. You do not know which samples counted, what happened during movement, or whether a trend is short-term texture or a daily summary.

RHRSpark separates the sources instead of smoothing them together. Recent views use heart-rate samples that Apple HealthKit labeled as sedentary. Longer views show Apple's own daily resting heart rate directly.

The result is simple: you always know what you are looking at.

The instrument

Calm enough to live beside the clock.

RHRSpark is built for repeated glances. The line shows the shape. The large value keeps the current signal legible. Dashes show where qualifying data is not available instead of pretending the gap is real signal.

RHRSpark displayed on an Apple Watch Ultra-style case with resting heart-rate complications.
Sedentary Short windows focus on samples marked sedentary, so movement does not quietly masquerade as rest.
Apple RHR Longer windows use Apple's daily resting heart-rate metric directly, clearly labeled as Apple's source.
Gaps When there is no qualifying data, the line shows a dash instead of filling the space with a guess.

Two sources, four windows

Short-term texture and long-term baseline stay separate.

8H

Sedentary heart rate

Recent sedentary samples make the last several hours visible without folding movement into the resting signal.

24H

Daily sedentary shape

The 24-hour view helps you notice how rest, work, illness, sleep, or stress show up across the day.

7D

Apple's daily RHR

A week of Apple's own resting heart-rate values gives the short-term line a steadier baseline.

30D

Longer RHR arc

The 30-day view shows drift and baseline movement without inventing a new hidden metric.

Design philosophy

Transparency is the feature.

"I wanted to see the actual shape of my resting heart rate throughout the day, not a single number derived from unknown samples at unknown times. When the line dips, I know why. When there is a gap, I know I was moving."

- the creator

Opaque appsOne daily number

RHRSparkSource-labeled sparklines

Opaque appsHidden sample selection

RHRSparkSedentary samples called out

Opaque appsFilled or smoothed gaps

RHRSparkDashes when data is missing

Opaque appsBlended interpretation

RHRSparkTwo sources, not blended

Who it is for

People who want the source, not the spin.

The self-tracker

You already notice how illness, sleep, recovery, and stress move resting heart rate. You want that signal closer to the surface.

The transparency advocate

You want to know what counted, what did not, and whether you are seeing sedentary samples or Apple's daily RHR.

The HRV companion user

Resting heart rate complements HRV naturally, broadening the picture without one metric trying to explain the other.

The data-over-decoration type

You do not need encouragement, warnings, or congratulation. You need the trend where you can see it.

Simple pricing

Start free. Unlock Pro once.

Free to download and try with three 24-hour complications. $2.99 one-time unlock for Pro: all 10 complications across four time windows. No subscriptions, no accounts.

RHRSpark Pro complications shown on Apple Watch.