Zabbix - Track, record, alert and visualize performance and availability of IT resources
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
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.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.