In sufficiently modern versions of Rails you could write:

    def index
      self.response_body = Enumerator.new do |socket|
        100.times do
          socket << "hello world"
        end
      end
    end

Your API is a little less verbose, I'll give you that, but I don't see why you need Queues and Threads unless the problem actually calls for those things. It still looks like you are writing to a socket either way.