Knock, Knock 1.0

Knock Knock is a network utility application living in your Mac OS X menu bar. It automatically checks the reachability of your network hosts on a regular basis. If there is a webserver running, Knock Knock is able to check the HTTP status response code for you as well.
*Stay up to date at all times*
Knock Knock provides a panel that stays on top of your other apps for an easy overview if any host is no longer available or comes back online.
*Easy setup*
It has never been so easy to keep taps on all of your domains, servers or even computers in your local network! Just enter a hostname or IP address, set the time between reachability checks and relax.
*Sky's the limit*
Check an unlimited amount of sites as often as you want and be the first to know when something is wrong - with your own sites or any other site on the web.
ProTip:
Make sure your websites return a status code greater than 400 if there are unexpected errors with your code, like timeouts or "unable to connect to database".