[joshvm]

Take a look at Particle. They sell dev boards, but also have excellent documentation on how to scale (at least they used to, I'm not sure where it's gone now - have a look in the datasheet section) - obviously they want to get you into their cloud fleet management platform, but it would be a tempting solution for me. For example, you buy the dev board (fairly cheap), they also sell the SoC (cheaper when you buy in bulk) and have design guidelines for making your own boards.

The boards themselves are quite nice. It's an Arduino-like stack and you can always code in C++ if you need the STM32 capability underneath. The main stack is also open source I think.

Doesn't really cover much on the mechanical side, e.g. enclosure design. That's a whole different game and that's where people lose a lot of money - if you mess up an injection mold for example.

https://www.particle.io/