PagerDuty - Cloud based monitoring service
CloudHealth - CloudHealth is IT service management for the cloud, enabling policy driven cost, utilization, performance and security optimization.
VictorOps - We make on-call suck less & help teams to solve problems faster.
CloudCheckr - CloudCheckr provides security, cost and usage reporting and analytics to help users manage their AWS deployment.
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.
Amazon CloudWatch - Amazon CloudWatch is a monitoring service for AWS cloud resources and the applications you run on AWS.