ZE Key Mapper allows you to use the full keyboard in your game. Rebindable keys will be available in the future.
This plugin allows the game developer to configure how each key interacts with the game. Keys are now checked by using strings, rather than Ruby's symbols, so changing each key is as easy as changing a parameter in the plugin's configuration.
Rebinding the keys is a planned feature, but it's currently unknown when that will be finished.