Openstrap Edge makes a WHOOP 4.0 band useful without a subscription
Article excerpt
The WHOOP 4.0 is a screenless fitness wearable designed for 24/7 continuous tracking. It focuses heavily on sleep quality, physiological recovery, and daily exertion levels rather than step counts. The tracker operates via a subscription model and is typically priced between $30/month and an annual fee of $239 Abdul Sahil isn’t knocking WHOOP. But the […]
The WHOOP 4.0 is a screenless fitness wearable designed for 24/7 continuous tracking. It focuses heavily on sleep quality, physiological recovery, and daily exertion levels rather than step counts. The tracker operates via a subscription model and is typically priced between $30/month and an annual fee of $239
Abdul Sahil isn’t knocking WHOOP. But the price stings.
When a membership lapses, the hardware is basically useless, You Own it, You still can’t use it, it just goes dark, because the app stops talking to it. So you’ve got a perfectly good sensor turning into a paperweight. That’s the only thing I set out to fix.
I spent a few weeks reverse-engineering how the 4.0 talks over Bluetooth, how it streams data, how to acknowledge its events so it keeps sending, how to capture and parse all of it. and built a small open-source stack around it. I tested the decoded values in different situations (wearing it, off-wrist, charging, workouts) and checked them next to my Apple Watch Ultra 1 to make sure they line up. I’m fairly confident in them, though I’ll say plainly I’m not claiming 100% certainty on everything.
The software is under an open MIT license and you can check it out on GitHub.