This is a very simple little dashboard I wrote a while ago when I needed something to check quickly when websites started going down to let me know whether a problem was localised or not.
I wrote this for running on my local webserver. It is most likely not secure to put on a public facing website, so if you must do that, please use some form of authentication.
Simply copy the files into a folder on your webserver and then add the websites you want to monitor to the websites array in index.html. That's it.
If you would like to tweak the representations of the HTTP codes, you can do that in get_status.php. The corresponding css classes are all declared directly in index.html.