We are operating one of the most popular free monitoring services called mon.itor.us (http://mon.itor.us) and many (25,000+) webmasters and IT people use it. We have got lots of positive feedback and we are going to enhance and provide more services for free. I would like to make a survey which kind of (free) systems, network and application monitoring and notification services and tools would make sense for people in this forum. Please post here what kind of problems you face and what would be useful for you.
I have used WebsitePulse and I found it useful (so all the features they have would be good in your tool) but here are some of the things that bugged me: Can't configure thresholds. They considered a third-party ad provider not responding quickly enough to be the same severity as the whole site going down. No attempt to measure user experience. A page won't display until all the css and js files in the <head> section have finished downloading. If js files are taking 10 seconds to serve this is much more serious than image files taking 10 seconds to serve. Lack of detail in alerting. They have a Firefox plugin that shows a red, green, grey or orange dot depending on the current status of the site. In practice, anything that was orange for more than two tests went to red anyway. More colours would have allowed more information to be taken in at a glance. Poor website. Logging in to their website and navigating to the reports about our websites was hell. New windows popping up all the time and links in the new windows would load back in the old window. Usually had to log in twice as it forget I was logged in after the first page loaded (sometimes up to 5 times in a row.) Things they did well: Checking from multiple locations around the world. Checking every 15 minutes. Keeping track of total uptime of website. Keeping track of page load times for every check. Creating a Firefox plugin to making notification of alerts very easy. Other services that I might find useful: Email server monitoring. (Both send and receive.) Blacklist monitoring. (If you're on one you want to know about it quickly.)
Are you checking to see if the domain is showing cpanel error? sometimes it displays the cpanel page instead of the home page. and sometimes mysql connection error. Please include all these features.