PagerDuty - Cloud based monitoring service
Obkio - Simple Network Monitoring and Network Troubleshooting software to empower users to identify and troubleshoot network & application slowdown from the end-user perspective.
VictorOps - We make on-call suck less & help teams to solve problems faster.
SolarWinds Network Bandwidth Analyzer - Download a 30-day free trial of Network Bandwidth Analyzer Pack, easy-to-use software that delivers real-time monitoring, alerting, and reporting for routers, switches, and other SNMP-enabled devices.
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.
SevOne - SevOne provides network managers with monitoring, troubleshooting, and performance reporting capabilities.