Here's a C/C++ partial implementation of posits:
https://github.com/Etaphase/FastSigmoids.jl
contains both a julia library and a C/C++ library. Posits are implemented as a C type and a C++ class where the type and class sizes correspond to the bitwidth.
FastSigmoids uses float and double types which would be problematic in embedded environments.
The next big TODOs are addition, substraction and rounding. Then advanced operations like sqrt, fma, etc. As part of the posit spec.
I've been working alone on that project, this being my first time working with floating point representation. I'm happy I could even get to that stage, and I hope someone can pick up my work and start contributing.