Thanks, I've personally found benefits from being to learn to control my breathing in stressful situations.

Right now it only works with the Polar H10, but it would be possible to adapt it if other chest strap monitors have an accelerometer in them.

what about an Apple Watch ? would it be possible to create an app for it ?

You might be interested in this https://www.59breaths.app/

Doesn’t let you measure HRV (so easily, as an application). If you mean using the Apple Watch as the sensor.

There’s a couple of HRV apps for iOS though.

You can get HRV data after a “mindfulness” session, but not in realtime during the session, at least as far as I know. That’s what I meant with not so easily.

I also found that the results don’t match measurements with a HR strap very well, at least for me.

The Apple Watch measured HRV when using the Breathe function in the Mindfulness app. Apps like Health, Training Today, and HRV Tracker can help visualize these readings.

Do you wear this chest strap under your clothes every day?

No, this is just for biofeedback training, so just for a session once a day

The literature is not particularly confident on the benefits of breathwork. A recent meta study found limited positive evidence. They conclude it can probably help some people, but the mechanism is unclear (and I read that as could be placebo). At least it's pretty safe. There's a lot of hype and the few studies that exist are potentially biased.

https://www.nature.com/articles/s41598-022-27247-y