I solved my problem brilliantly with the proxylocal gem at http://proxylocal.com.
Simply install the gem. In Terminal type $proxylocal 3000
Then your server is available to your mobile or any other device at something like http://fp9k.t.proxylocal.com/
You can make it available at something more user friendly by opening another window in Terminal and typing: $proxylocal 3000 --host testhost
Then your site will be available at http://testhost.t.proxylocal.com/