Happy to announce that I finally got off my butt and built a full-fledged Kodi
driver for Elve.
The source code is available on GitHub
and I've attached the .dll and an installer to this post.
The driver uses a combination of JSON RCP (over TCP socket) push notification and HTTP polling so the responsiveness to major events (play, pause, volume change, etc) should be pretty good. I based the JSON RPC calls on the Jarvis JSON Introspec so I'm not sure if it will work properly with early versions of Kodi.
Please let me know if you run into any issues or have any questions.