Want to restart your Rails development server whilst you work? Now you can!

guard 'rails', :port => 5000 do
  watch('Gemfile.lock')
  watch(%r{^(config|lib)/.*})
end

Four fun options!

• :port is the port number to run on (default 3000)
• :environment is the environment to use (default development)
• :start_on_start will start the server when starting Guard (default true)
• :force_run kills any process that's holding open the listen port before attempting to (re)start Rails (default false).

This is super-alpha, but it works for me! Only really hand-tested in Mac OS X. Feel free to fork'n'fix for other OSes, and to add some real tests.