I'm looking for a wristband/watch/"thing on the arm" with GPS, heart monitor and pedometer(accel+gyro).
I looked at what is on the market, but sending my bio metrics to fitbit or garmin servers is not something I want to do.
Is there a fitness tracker band that is hackable in a sense that I can get the data out of it without proprietary software? I don't mind the firmware being closed source, as long as there is no LTE. I just want to sync and manage my data myself.
I don't think you need to enable sync, so keeping the data local wouldn't be an issue. AFAIK, you should just be able to use the Garmin Connect software once to set up the watch, and that's it.
The great thing about the Garmin watches is that pretty much any fitness hardware that uses ANT+ will work with them. ANT+ is also an open protocol so you're not locked in with a specific manufacturer.
[1]: https://www.thisisant.com/resources/fit