Prometheus - An open-source systems monitoring and alerting toolkit.
Dynatrace - Cloud-based quality testing, performance monitoring and analytics for mobile apps and websites. Get started with Keynote today!
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.
Microsoft System Center - Microsoft System Center provides solutions to simplify the deployment, configuration, management, and monitoring of the infrastructure.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
StatsD - Simple daemon for easy stats aggregation.