Gadgetbridge

Gadgetbridge is an Android application that lets you use your Bluetooth gadgets, mostly wearables like smart watches but many more, without the vendor's closed source application, and without creating an account or sending any of your data to the vendor's servers. Its home is on Codeberg; the GitHub copy is a mirror.

Gadgetbridge runs on the phone and talks directly to a supported gadget over Bluetooth, standing in for the vendor's own app. Which devices are supported, and what each one can do through Gadgetbridge, are listed on the project's own Gadgets and Features pages, since support differs by device and model.