ERALION

Monitoscope is a webservice that monitors websites and alerts in case of access failure, it allows up to monitor 1 free website.

Monitoscope

Get alerted when your website go down with Monitoscope.

ApplicationInsights

Integrates a WordPress site with Microsoft Application Insights. More information about Application Insights can be found <a href="http://azure.microsoft.com/en-us/documentation/articles/app-insights-get-started/" rel="nofollow ugc">here</a>.
Active development is done on <a href="https://github.com/Microsoft/AppInsights-WordPress" rel="nofollow ugc">GitHub</a>.
Other SDKs and documentation can be found <a href="https://github.com/Microsoft/AppInsights-Home" rel="nofollow ugc">here</a>.

Application Insights

I'm sure this feature is incredibly helpful, but this plugin has not been maintained in over 2 years, and it's age is showing. When I'm debugging other issues, I'm constantly getting PHP notices that functions aren't being used correctly. It's helpfulness is severely outweighed by it's lack of maintenance and support. Avoid this plugin if you can.

Only Causes Me Headaches

Integrates a WordPress site with Microsoft Application Insights.

Monitoscope vs Application Insights