

I have been using a BangleJS 2 for the last year, and have quite liked it. There is a companion app, Gadgetbridge, to install on your phone, which is available through F-Droid (there is a Bangle-specific version of it, or a generic version that supports a bunch of other smart watches). There is also an app store (all free software) for apps that run on the Bangle itself. It includes a heart monitor, but no music streaming.
I’ve also been watching rePebble as they start making new Pebble smartwatches. I’ve never owned one, but a lot of people swear by them. They are now fully open source and have an app store. No idea if they can stream music.




Actually, it’s more the opposite. Sorry, I don’t think I explained too well. The watch works just fine on its own without a smartphone. For functions that require phone and watch working together, Gadgetbridge lets them communicate (e.g. when you receive a text message on your phone, Gadgetbridge will let you read the text on your watch).
The apps on the watch will work with or without a smartphone. However, installing apps from the Bangle app loader requires the watch have a Bluetooth connection to a phone or computer. After apps are installed, they will run even without the Bluetooth connection.
Finally, note that the Bangle does not have an internet connection on its own; it has no cellular or wi-fi radios on board. So any apps that require a network connection (e.g. weather) will only work when paired to a phone with Gadgetbridge. I think there are other watches with wi-fi, but I’m not familiar with them.