format_helper.rb

module FormatHelper
  
  def boolean_flag(bool, text = nil)
    "<span class='flag #{bool.to_s}#{ ' labeled' unless text.nil?}'>#{text || bool.to_s}</span>"
  end
  
  def yes_or_no(bool)
    bool ? 'Yes' : 'No'
  end

end

view.haml

%table.lite{:cellspacing => '15'}
  %tbody
    %tr
      %th Complete?
      %td.main= boolean_flag(@idea.complete?, yes_or_no(@idea.complete?))