This was a project I implemented for fun to try to understand how Raft works (and also get more practice with Rust). The basic idea is that some state gets synchronized between 3 browser windows (currently hard-coded) over WebRTC. It's pretty fast if you're on the same machine (I've seen ~2000 writes/second on Chromium).
It's probably not useful for real applications in its current form, but I could potentially see some use cases in peer-to-peer browser applications.