AppBeat is reliable website monitoring service that alerts you when there is a downtime or failure. It also measures performance and provides functional tests…

Monitis is a web performance monitoring platform.

PHP Server Monitor is an open source tool to monitor your servers and websites.

Pingoscope is a website monitoring site.

StatusCake delivers accurate global website monitoring for tens of thousands of customers.

WebSite-Watcher detects website updates and highlights all changes in the text.

HappyApps is an online app uptime monitoring platform.

NetCrunch is a Windows Server–based network monitoring tool that boasts high performance and impressive scalability even in a single-server deployment.

Pingdom helps you give your customers the best possible web experience by offering a Powerful Web Performance Monitoring Solution.

Port Monitor is an easy tool that does website and server monitoring 24/7 every 60 seconds for free.

Uptrends helps you monitor your website uptime, so you will get an alert whenever your websites goes down.