There are a couple of prototypes for dyadic (two-party) session types (
nemo) but they don’t seem to be under active development.
For implementations of multiparty session types there are several prototypes to look at in various other languages, so far I’ve found examples in Ocaml, Scala, C, Python, Erlang, and (recently) Go. Of those the C and Go implementations are probably closest to what I would expect to see in Rust, although both rely on external verifiers in other languages (Python Scribble for Session C and Haskell Gong for Go/MiGo).
What I would like is to be able to set up a pre-defined topology of threads and channels and statically verify some nice properties to have such as deadlock freedom, communication safety, etc.