Visualping - Visualping is the easiest to use website checker, webpage change monitoring, website change detector and website change alert software of the web. Read more about Visualping.

Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.

Distill Web Monitor - Distill is a web monitoring tool. It can monitor RSS feeds, a webpage or a part of webpage. Alerts in the form of pop-up, audio or emails can be received.

Platypus - Realtime server monitoring and reporting

WebSite-Watcher - WebSite-Watcher detects website updates and highlights all changes in the text. WebSite-Watcher monitors web pages, password protected pages, disucssion forums and much more.

Nagios - Complete monitoring and alerting for servers, switches, applications, and services