I'm waiting for the 2020 edition of the TTGO T-Watch, then I'll do another rewrite from the ground up with better code and hopefully support for external apps.
At this point, you have to really look at it and say actually, this'd be really good for robotics - esp32, add a motor shield, 6axis sensor, motion depth sensor, k210 with camera, wifi, BT, lipo capable, grove connector, all in one unit!
Even the product page has an idea for a robot on it...
There's also heaps of daughterboards and even a keyboard add-on!
The open-source AmigaOS is called AROS.
It has its own problems; Messy licensing and poor support for the real (68k Amiga) hardware are two of them.
I haven't worn a watch in forever and now I kinda want to..
They're interesting bits of hardware and worth playing with. The sample code on which the phone was originally based is quite... convoluted for what it is. I'm going to spend some more time playing with FreeRTOS and seeing if I can build something a bit more professional after looking at the Rebble code.
However, the most important question : is your partner using the watch or ordered one?
If you don't have an Amiga you can use AROS on your PC or in a VM that is the open-source version of AmigaOS 3.1 rewritten: https://aros.sourceforge.io/
Also, the Oscilloscope Watch is supposed to be shipping now, finally. That's gonna be a hard watch to not add a synthesiser module to.
If you order one, you'll need to use the Arduino IDE and install the libraries listed on the Github but it's all done over USB so it's pretty easy. If anyone wants to buy a black one, I'd really appreciate it if they used my banggood affiliate link: https://www.banggood.com/custlink/3GKvwc2lad but do check the price against Aliexpress first as one may be cheaper than the other.
While I'm not big on the 1.X color scheme and UI, it should be easy to go from this to 2.X style.