There will eventually be an accompanying project with a real controller written using this.
Gem: https://rubygems.org/gems/maniaplanet-rpc
Repository: https://github.com/Speljohan/maniaplanet-rpc
Enjoy!
EDIT:
Just a quick note that (i think) it now handles the entire spec, including callbacks. Feel free to try it out, and don't forget to report issues on the github tracker, so that i may look into them
