Zabbix - Track, record, alert and visualize performance and availability of IT resources
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
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.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.