Session Debugger (put in application_controller.rb). Courtesy of Jason Waldrip.

gistfile1.txt

  def session_with_debug
    SessionDebugger.new(session_without_debug)
  end

  alias_method_chain :session, :debug

  class SessionDebugger < SimpleDelegator

    def []=(key, val)
      puts "#{caller.first} SET session:#{key} TO #{val.inspect}"
      super
    end

  end