xip.io is a special DNS service which can allow you to test virtual hosts from other devices on your internal network (say, iPads, phones, etc). The use-case might be if you have multiple vhosts on a single IP address (e.g., 10.0.0.1), so just plugging the IP into your URL bar won’t get you the correct vhost.
This would allow you to test the vhosts from devices that don’t have hosts files, without having to set up your own internal DNS server.
