Zabbix - Track, record, alert and visualize performance and availability of IT resources
Garden - Container Engine
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.
Affinity - Relationship Intelligence, Reimagined
Prometheus - An open-source systems monitoring and alerting toolkit.
Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.