In the past I would just use my iPhone's email-to-txt email address. However, when I received the txt message, it wasn't formated very pretty, and it would have a different "From Number." So if we had a crazy day, I would have 20-30 message threads in my iPhone all about Nagios. [...] What I like out this setup is with Twilio, I can buy a phone number for $1 a month. So all my notifications come through the same number.

He's included the PHP code he uses to send the notifications (using the Twillo library) and the Nagios commands he configured to send the notifications to that script via the command line.

Real-time web applications are networked applications, with web-based user interfaces, that display Internet information as soon as it's published. Examples include social news aggregators and monitoring tools that continually update themselves with data from an external source. In this tutorial, you will create Pingstream, a small notification tool that uses PHP and JavaScript to communicate over the Extensible Messaging and Presence Protocol (XMPP), a set of XML technologies designed to support presence and real-time-communications functionality.

You'll need to already have the usual software installed - PHP, Apache and MySQL - as well as a few others: Openfire, jQuery, Strophe, XMPPHP and LastRSS. They introduce some of the concepts behind real-time messaging, the XAMPP protocol and, of course the code to show how to create their service.