Concurrent FRP implemented in Rust.
If you're not familiar with Elm or the design behind Evan Czaplicki's Concurrent FRP, you should read Elm: Concurrent FRP for Functional GUIs or watch his talk at StrangeLoop 2014.
This codebase is larger and more complex than some similar libraries (frp-rust, carboxyl, rust-frp etc) becasue it handles concurrency (and because I'm a Rust newb). Simplification suggestions welcome!