I've avoided fitness wearables for years, and it was never the price that stopped me. It's that every one of them works the same way: the sensors go on your body, and the data goes to someone's server. Heart rate, HRV, sleep stages, recovery — arguably the most intimate data you generate all day — handed to a company, forever, as a condition of using hardware you paid for. WHOOP is the extreme version of this. The band literally does nothing without their cloud.

So when I found Edge I actually got excited, because it breaks that model completely.

It's a new open-source app (MIT licensed) that pairs with a WHOOP 4.0 band over Bluetooth and does everything locally on your phone. It decodes the band's data itself and computes sleep, recovery, strain, HRV and the rest on-device. No account, no signup, no subscription, and no server that ever sees a single heartbeat. That's not a privacy setting buried in a menu — there's just no cloud component at all.

The fun part: since lapsed-subscription WHOOP bands are basically e-waste for their original owners, used 4.0s go cheap secondhand. So you can pick up the hardware, never give WHOOP an email address, and have a full health tracking setup where the data physically cannot leak because it never leaves the device.

Other things I like:

• The metrics come from published, peer-reviewed methods with citations in the code, not some black-box model.
• Every metric has a confidence rating, and when the data isn't good enough you get a dash instead of a made-up number.
• The whole protocol is documented in their research repo, so the "nothing leaves your phone" claim is auditable, not marketing.
• The dev takes crypto donations. I asked him about XMR and he said he'll have an address up by tomorrow — make of that what you will.

One caveat in the interest of full honesty, since this crowd will find it anyway: the GitHub release builds send anonymous crash diagnostics by default (you can turn it off), store builds send none. Neither ever includes health data.

It's early beta and built by one person, so expect rough edges. But the architecture is exactly what I've been waiting for in this category.

Standard disclaimer: I don't own it, don't contribute, don't know the dev beyond that one exchange. Just sharing because this is the first time I've seen a wearable setup I'd actually consider using.

Repo: github.com/OpenStrap/edge
Site: openstrap.site

So for everyone else who skipped wearables over this stuff — does on-device-only change the math for you? Would you actually pick one up now, or is the hardware itself still a dealbreaker?