On one hand I'm quit surprised this didn't already exist, but on the other hand I can't see a huge market for it?
I can imagine non-C++ libraries (e.g. Python or Ruby) wrapping the C++ interface rather than using a custom implementation.
In fact from personal experience of the Node one the SDK uses the API descriptor to generate the client (Which makes unit testing it tricky incidentally, but I digress).
It is somewhat similar in concept
Most good libraries written in C++ that are meant to be used as libraries in other languages expose a C interface. I don't see a C interface in their docs.