Platypus - Realtime server monitoring and reporting
NewRelic - New Relic is a Software Analytics company that makes sense of billions of metrics across millions of apps. We help the people who build modern software understand the stories their data is trying to tell them.
Monitornator - Server monitoring made simple
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.
AppDynamics - Get real-time insight from your apps using Application Performance Management—how they’re being used, how they’re performing, where they need help.