Ability to define the IP that should be used for a web check
For Example:
There are Web Servers 1 - 10 and all output the same content I would like to sanity check, all those webservers are behind a loadbalancer and the ip of $DOMAIN points to the loadbalancer
So no etc/hosts entry would solve that problem and usually servers are setup the way that if you request $DOMAIN without using exactly $DOMAIN (for example, use $IP directly) you will get a 301 redirect to $DOMAIN