Android · Polar H10

Your Polar H10 ECG, all night.

Built by a heart patient who was refused the recorder his specialist prescribed, and recorded his own nights instead. The trace, the numbers and a mark for the moment you feel something. Everything stays on your phone.

Get it on Google Play Why it exists

Free to record and share. Android 8.0 or newer. The app has no internet access.

Live ECG

Recording

0:02:24

−5 s−4−3−2−1now

Why it exists

In June 2026 my defibrillator fired. The episodes that followed were too small for it to act on, and insurance refused the recorder my electrophysiologist prescribed.

So I wet a Polar H10 strap, wrote an app that saved every sample it sent, and slept with it on. Night after night. When I ended up in the emergency room on 9 August, the whole episode was on my phone, from the first odd beat to the moment the staff took over. I handed it to them as a file their software could open.

Fairest Heart is the general version of that recorder. It records, shows and shares. The analysis I built for my own heart was tuned to one heart and stays with me; what you get is the plain record, in open formats, to hand to whoever you choose.

Dirk Fairest, maker · Read the whole story →

130samples per second, every one saved

6 hchunks, so a crash costs minutes, not the night

EDF+the file format hospital software opens

0servers, accounts, uploads

Heart rate i

76bpm

last minute 67–76

Strap signal i

Good

97.2 % readable

HRV i

42ms

RMSSD, this night

Marks i

with a diary note

The figures above are an example night, not yours.

What you get

It records, shows and shares what the strap provides. Nothing is interpreted for you.

Single-lead ECG at 130 samples per second, heart rate, R-R intervals, HRV, strap contact and motion. You see the trace and the numbers, and you decide whom to share them with.

Live ECG trace

Heart rate and HRV while the strap is on. A 5, 10 or 30 second window, the standard 25 mm/s grid.

All night, phone locked

Overnight and all-day recording in six-hour chunks. A notification keeps it alive and carries the mark button.

A mark when you feel it

One tap saves the moment. Add a diary note later: what you felt, when, and how long.

Recording viewer

Any night on a 25 mm/s × 10 mm/mV paper grid with zoom, the marks lined up, 30 seconds before each.

Your day and night

Heart rate over the day, resting heart rate, HRV, time in training zones, a sleep estimate from the strap, signal quality, Poincaré plot.

Share, in open formats

EDF+ (the format most ECG software reads), CSV, or a PDF with strips at your marks and the whole recording.

How it works

Three steps, then sleep.

Wet the strap, put it on

Any Polar H10 that streams ECG. The app finds it over Bluetooth and connects.

Recording starts on connect

Lock the phone. The night is written to the phone as EDF+ and CSV, with a copy in Downloads.

Look, mark, share

In the morning: the trace, the numbers, your marks. Share a PDF or the raw file with whoever you choose.

No strap yet?

Fairest Heart works with the Polar H10 chest strap. Nothing else is needed.

Any generation that streams ECG. It runs a year on one CR2025 coin cell.

Polar H10 chest strapSee on Amazon

→

CR2025 batteriesSee on Amazon

→

As an Amazon Associate I earn from qualifying purchases.

Fairest Heart is not a medical device. It records, displays and exports the data your sensor provides and does not analyse your heart rhythm. If you are worried about your heart, see a clinician.

Plans

Free records and shows. Plus shares. Pro holds the long view.

Every plan records and shows the same signal. EDF+ and CSV sharing are always free.

Free

Records

Live ECG, heart rate, strap signal
All-night recording with marks and diary
Keeps your newest 24 recorded hours
Share as EDF+ and CSV
Baseline and time in training zones

Plus

$4.99 / month

or $29.99 a year

Everything in Free
Keeps seven days
PDF with strips at your marks and the whole recording
Live R-R, HRV and pNN50 tiles under the trace
Depth views: Poincaré and the day's R-R, HRV and pNN50

Pro

Holds the long view

$9.99 / month

or $59.99 a year

Everything in Plus
Keeps every recording
Trend across nights
One-tap backup of new recordings

Prices shown in US dollars; Google Play shows the price for your country. Subscriptions renew until cancelled in Google Play. See the terms.

“I wanted a plain record of my own nights that I could hand to whoever I chose. Now you can have one too.”

Made by one person

Fairest Heart was built by its first user, between medical appointments, with AI assistance. There is no company behind it beyond the one that publishes it, no server, no analytics and no account.

The story → · Write to us →