I'm looking at buying readily available a cheap programmable smartwatch. PineTime was easy to write programs for and that Casio replacement board [0] discussed here earlier also hade a nice tool chain, but with shipping and taxes it's just too bothersome.
I bought into the Bangle.js 2 Kickstarter and I have to say, I'm incredibly happy with it. Granted, I've done nothing with it besides design my own watch face and take advantage of the GPS to set the time occasionally, but I know it's capable of a lot more. It was very easy to write the watch face code, and I feel like it would be pretty easy to do whatever I wanted to do. Ecosystem for it is probably a bit more developed than it was at launch, too- they were supposed to follow up with some apps that made interfacing it with your phone easier, dunno where that ended up.
To be fair- I've also got PineTime bookmarked for if my Bangle.js 2 ever breaks, or I just want to mess around with some lower-level aspects of watch firmware.
There is an emulator on the web, so develop something simple and the order one. I wanted to buy ten watches so Bangle.js was not an option, but if you just want something programmable I do recommend it.
Their "app store" is online [0] and you can actually review the source code for all of the apps on it by clicking the github icon on each entry, here's one for example [1]
[0] https://www.crowdsupply.com/oddly-specific-objects/sensor-wa...