I just wrote this. Now I understand why it's a thing. BECAUSE IT'S COOL.

observable.rb

module Shortwave
  module Observable
    def self.included(base)
      base.send :include, InstanceMethods
    end

    module InstanceMethods
      class Notification
        attr_accessor :event, :id, :klass

        def initialize(record)
          klass = record.class.underscore
          id    = record.send(record.class.primary_key)
          event = record.new_record? ? :created : :updated
        end

        def routing_key
          "#{klass}.#{id}"
        end
      end

      def notify(record)
        notification = Notification.new(record)
        Shortwave.broadcast(notification.routing_key, notification.event)
      end
    end
  end
end