Using http://www.youtube.com/watch?v=B1l5F3KEEBw as inspiration after being sick of modifying all the Devise templates by hand.

views.rake

namespace :views do
  desc "Converts all .html.erb files in app/views to .html.haml files"
  task :hamlize do
    Dir.glob('app/views/**/*.erb').each do |file|
      begin
        puts "Hamlizing #{file}"
        `bundle exec html2haml #{file} | cat > #{file.sub(/(\.html)?\.erb$/, '.html.haml')} && rm #{file}`
      rescue => e
        puts "Error in #{file}: #{e.message}"
      end
    end
  end

  desc "Adds .row .large-12.columns at the top of all .html.haml files in the specified folder under app/views. Specify the folder to start in as FOLDER."
  task :zurbify do
    if ENV['FOLDER'].blank?
      puts "Specify a FOLDER in app/views to start searching for files"
    else
      Dir.glob("app/views/#{ENV['FOLDER']}/**/*.html.haml").each do |file|
        begin
          contents = File.read(file)
          unless contents.include?('.row') && contents.include?('.columns')
            puts "Zurbifying #{file}"
            File.open(file, 'w') do |f|
              f.puts '.row'
              f.puts '  .large-12.columns'
              contents.each_line do |line|
                f.puts "    #{line.sub(/\r?\n$/, '')}"
              end
            end
          end
        rescue => e
          puts "Error in #{file}: #{e.message}"
        end
      end
    end
  end
end