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.
StatCounter - StatCounter is a simple but powerful real-time web analytics service that helps you track, analyse and understand your visitors so you can make good decisions to become more successful online.
AppDynamics - Get real-time insight from your apps using Application Performance Management—how they’re being used, how they’re performing, where they need help.
AFSAnalytics - AFSAnalytics.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Histats - Start tracking your visitors in 1 minute!