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.

NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.

Dynatrace - Cloud-based quality testing, performance monitoring and analytics for mobile apps and websites. Get started with Keynote today!

Server Monitoring - A server monitor is a tool that monitors your server and website on close intervals and reports to you if it's inaccessible.

LogicMonitor - LogicMonitor is the SaaS performance monitoring platform for the world's best IT teams. Deploy Fast, Monitor More, Improve Ops.

Nodeping - NodePing Server Monitoring and Web Site Monitoring. Simple but powerful Internet service monitoring.