I recently used http://yeoman.io/ http://yeoman.io/ for developing a backbone.js app, you can easily set it up to automatically compile (it uses Grunt internall

I recently used http://yeoman.io/ http://yeoman.io/ for developing a backbone.js app, you can easily set it up to automatically compile (it uses Grunt internally) the individual sources to your rails apps public folder for development, and then compile/minify/concatenate your files for production. Worked quite well for me.