I'm curious if anyone has tried one of the newer e-ink smart watches you see on Alibaba, which use ESP-32 or other low-power SOCs. I saw one recently at a meet-up and the guy who was wearing claimed it was completely open-source and he could run whatever he wanted to on it. It did not have heartrate monitoring or anything other than clock on it, as far as I could tell.
Not only can you run anything you want on it but it supports the Arduino IDE and Micropython. I assume all of the Alibaba ones are based off of Watchy.
The biggest issue is the software. It's mostly abysmal. The best effort I've seen so far has been InfiniTime for the PineTime. It's very difficult without full-time employees working on improving things.