Dejal Systems last week released Simon 2.2 [1], the latest version of the company's Internet service monitoring tool, which can also check for content updates to Web pages. Notable in 2.2 is the addition of a Script service that enables Simon users to create their own specialized tests using AppleScript, shell scripts, Perl, PHP, Python, Ruby, or any other scripting system available at the command line. The Basic service, for checking Web sites, now supports checking https, feed, and file URLs; can check forms that use POST as well as GET, and remembers and uses cookies. Other changes include a new MySQL service, a Specific DNS service for looking up a domain name with a specified DNS server, a Growl notifier, numerous interface tweaks, and a variety of bug fixes, among much else (see the full release notes [2] for details). Simon 2.2 is now a universal binary; upgrades are free to registered users, and new copies cost $30 to $200, depending on the number of tests.
Although we don't have that many servers to test with Simon, it has worked well in my usage, alerting me promptly when something goes awry and when it returns. And since it's often checking while I'm asleep, I particularly appreciate its flexible notifiers, which can, for instance, speak alerts, but only during work hours.
[1]: http://www.dejal.com/simon/
[2]: http://www.dejal.com/simon/release/