CodeGuard - CodeGuard provides website backup, monitoring, and malware remediation services to small and medium businesses.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Amazon AWS - Amazon Web Services offers reliable, scalable, and inexpensive cloud computing services. Free to join, pay only for what you use.
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.
Prometheus - An open-source systems monitoring and alerting toolkit.
PagerDuty - Cloud based monitoring service