Nagios - Complete monitoring and alerting for servers, switches, applications, and services
PagerDuty - Cloud based monitoring service
Gitwin - Enable your Windows system as a powerful and secure Git repository. Supports ssh, http(s) transports. Gitweb with highlighter and gravatar support available.
VictorOps - We make on-call suck less & help teams to solve problems faster.
NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.
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.