If the plan is to use an existing watch for a base, I'll just toss in the TK78G: https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&tab=all&SearchText=tk78g It may be on the way out (it's mostly disappeared from AliExpress) but it has some features that make it an interesting blend of B1 and B2: NRF52840, two physical buttons, GPS, Thermometer (external), heart rate sensor, accelerometer, touch screen and a nice 1.6" screen. I have it running Espruino right now (in the process of RE the screen and sensors). It may not replace the B2's always-on display, but it may be a replacement for B1?
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
If the plan is to use an existing watch for a base, I'll just toss in the TK78G: https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&tab=all&SearchText=tk78g It may be on the way out (it's mostly disappeared from AliExpress) but it has some features that make it an interesting blend of B1 and B2: NRF52840, two physical buttons, GPS, Thermometer (external), heart rate sensor, accelerometer, touch screen and a nice 1.6" screen. I have it running Espruino right now (in the process of RE the screen and sensors). It may not replace the B2's always-on display, but it may be a replacement for B1?