Intruder - Intruder is a security monitoring platform for internet-facing systems.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
HackerOne - HackerOne provides a platform designed to streamline vulnerability coordination and bug bounty program by enlisting hackers.
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.
Nessus - Nessus Professional is a security platform designed for businesses who want to protect the security of themselves, their clients, and their customers.
Prometheus - An open-source systems monitoring and alerting toolkit.