Nessus - Nessus Professional is a security platform designed for businesses who want to protect the security of themselves, their clients, and their customers.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
ManageEngine Desktop Central - Desktop Central is a Desktop Management and Mobile Device Management Software for managing desktops in LAN and across WAN and mobile devices from a central location. It supports managing Windows, Mac and Mobile devices running iOS 4 and above
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.
Rapid7 Nexpose - Network vulnerability and risk management solution.
Prometheus - An open-source systems monitoring and alerting toolkit.