Pingdom is a service that tracks the uptime, downtime, and performance of websites. Based in Sweden, Pingdom monitors websites from multiple locations globally so that it can distinguish genuine downtime from routing and access problems.

DF Site Monitor
DF Site Monitor - is a system for monitoring web sites. The system allows monitoring the availability of web sites and their content by checking whether the given content exists or does not exist on the site. The system can be used autonomously or as a module for other systems. For acquaintance...
Site Uptime Enterprise
☆☆ Deploy your Pingdom Clone site monitoring SaaS platform at an affordable price! Site Uptime Enterprise is a ready to run uptime monitoring solution that allows you to offer free as well as paid membership services that monitors your members' web sites as well as POP3 email server, FTP...
Uptime - Website Uptime Monitoring
Uptime is a comprehensive website uptime monitoring service which you can use to monitor any number of websites around the world.