Yes, i know!

Helpers are modules that provide methods which are automatically usable in your view.
But somtimes you want to use it in controllers ;)
This is my solution. Helpers are available in module named 'Helpers', so they don't brake anything. All rails helpers and named routes are included by default.
This is simple usage:

class ExampleController < ApplicationController
  include_helper ApplicationHelper, PicturesHelper

  def show
   ...
   flash[:notice] = Helpers::flash_with_picture('Hello from helper')
   ...
  end
end
And method to add to ApplicationController class.

class ApplicationController < ActionController::Base
  def self.include_helper(*args)
    require 'action_controller/integration'
    class_eval do
      helpers = const_defined?('Helpers') ? const_get('Helpers') : Module.new do
        @@controller = ActionController::Integration::Session.new
        def self.method_missing(method, *args, &block)
          if @@controller && method.to_s =~ /_path$|_url$/
            @@controller.send(method, *args, &block)
          else
            raise NoMethodError, "undefined method `#{method}' for #{self}"
          end
        end
      end
      ActionView::Helpers.constants.each do |constant|
        helpers.extend ActionView::Helpers.const_get(constant) if ActionView::Helpers.const_get(constant).instance_of?(Module)
      end
      if args.instance_of?(Array)
        args.each do |helper|
          helpers.extend helper if helper.instance_of?(Module)
        end
      elsif args.instance_of?(Module)
        helpers.extend args
      end
      const_set( 'Helpers', helpers ) unless const_defined?('Helpers')
    end
  end
end