Zabbix - Track, record, alert and visualize performance and availability of IT resources
Callmama - Get cheap international calling, international virtual number, Call Mama Gives an added advantage to send message and make calls to non-user of Callmama App.
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.
CallHippo - Easy to use Phone System with World-Class Support
Prometheus - An open-source systems monitoring and alerting toolkit.
KrispCall - Virtual cloud phone system for business