A slight refactor of http://lachstock.com.au/code/mobile-pages-in-sinatra/

mobile_helper_sinatra.rb

helpers do
  def mobile_request? 
    [ /AppleWebKit.*Mobile/, /Android.*AppleWebKit/ ].any? {|r| request.env['HTTP_USER_AGENT'] =~ r}
  end
  def mobile_file(name)
    File.exist?("#{options.views}/#{name}#{@mobile}.haml") ? :"#{name}#{@mobile}" : name.to_sym
  end
  def partial(name)
    haml mobile_file("_#{name}"), :layout => false
  end
  def deliver(name)
    haml mobile_file(name), :layout => :"layout#{@mobile}"
  end
end

before do
  @mobile = mobile_request? ? ".mobile" : ""
end