hostkeeper is a Vagrant box that comes with a DNS server (dnsmasq) and a web interface to provide an easy way to manage network-wide DNS emulations (or modifications) during local web development phases. Usually you need to adjust the "/etc/hosts" file on your OS X or Windows machine to test your local project with productive domains. However, this approach won't work on a (non jailbreaked) iPhone which has no direct file system access. Once the DNS in your network settings is set to the IP of the hostkeeper Vagrant box, all DNS requests from said device will obey the "faked" ones from hostkeeper, hence you can surf via Safari to "http://reddit.com" but don't end up on the productive web server of "reddit.com". Instead you end up on your local development box, since you added a mapping for that in the hostkeeper web interface.