Platypus - Realtime server monitoring and reporting
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
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.
Instatus - Quick and beautiful status pages.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
ContainIQ - Kubernetes native monitoring instantly