To monitor more than uptime and service availability, the high end of this is automated performance measurement analysis by Keynote Systems (keynote.com). They

To monitor more than uptime and service availability, the high end of this is automated performance measurement analysis by Keynote Systems (keynote.com). They have a lower end product called http://redalert.com/ http://redalert.com/ (formerly its own service) which is comparable to pingdom.