Why I built my own workout tracker
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I like building my own stuff. And I care about where my data goes.
Those two things are most of the reason this exists.
For a while I tracked my workouts in a well-known app. It did the job. But it wanted an account. It had a paywall waiting behind some features. And every rep I logged went up to someone else’s server.
Which, fine, it’s not state secrets, it’s how much I bench. But it’s still my stuff, and I didn’t really see why it needed to live anywhere but my phone. If it can just sit on my device, why not?
So I went looking for an open-source alternative. Something with no accounts, no paywall, and no cloud. Data stays on my machine, full stop.
I didn’t find one.
There are open-source workout trackers out there. But my needs were specific:
- Good UX. I’m using it mid-set, sweaty hands, resting between sets. It has to be fast and clear or I won’t use it.
- Apple Health and Apple Watch integration. Control a workout on my wrist, have it show up on the Lock Screen, read my heart rate.
- Local only. No server, no account. My data never leaves the device.
Nothing checked all three boxes. The polished apps were closed and cloud-first. The open ones didn’t have the integrations or the polish. The thing I wanted just wasn’t there.
So I built it. It’s called Ischys — ἰσχύς, Ancient Greek for strength.
What it actually is
Ischys is a workout tracker that runs entirely on your phone. No sign-up, no backend, no cloud. You install it and start tracking immediately.
The whole app is self-contained. It’s React Native, with a local SQLite database on the device. All the training logic — volume, estimated 1RM, personal records, streaks, charts — runs in TypeScript right there on the phone. There’s no server to send anything to, because there is no server.
That’s the part I like most. There’s no server, so there’s nothing to sign into and nothing to leak — your data just lives on your phone. It backs up with your normal iCloud backup, and you can export a full copy — JSON or CSV — whenever you want. It’s yours.
It also does the things I actually needed:
- Log sets (weight × reps), with warmup, drop, and failure set types, and a rest timer.
- Routines that prefill from your last session, so progressive overload is just there in front of you.
- Personal records detected when you finish, with history and charts per exercise.
- Apple Watch companion to mirror and control a live workout, a Live Activity on the Lock Screen, and Apple Health — heart rate in, workouts out.
- A catalog of 736 exercises bundled right into the app.
The design is deliberately plain. Monochrome, near-black, sharp, easy to read mid-set. There’s one bit of colour in the whole app, and it’s reserved for one thing: completing a set.
It’s open, and it’s live
Ischys is MIT-licensed. Clone it, build it, change it, run it on your own phone. The whole thing runs on-device either way.
It’s also on the App Store, free. It’s iPhone-first today — the headline features (Watch, Live Activity, Health) are all Apple-specific, so that’s where it started. Android is on the list, and I’d love to get it there.
This is the open-source workout tracker I went looking for and couldn’t find. So I made it.
It’s live now. Go try it.