Zabbix - Track, record, alert and visualize performance and availability of IT resources
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.
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.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
LogicMonitor - LogicMonitor is the SaaS performance monitoring platform for the world's best IT teams. Deploy Fast, Monitor More, Improve Ops.
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.