I have an OG pebble steel and it does everything I currently want in a smartwatch. I don't expect it will stop working for some time, and I plan on using it as long as possible.
EDIT: there's also this post on the tech specs on reddit[0]. This looks pretty re-implementable if you're a hardware engineer looking to do something fun. The right component mix seems to have been figured out already.
Firmware can be reversed, and as for the hardware, I suppose the teardowns iFixit did should be enough for a competent hardware engineer to replicate the design.
