Loggr - Loggr offers cloud-based, real-time Web Application Monitoring, which includes monitoring application events and users with ad-hoc analytics and notification system.

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.

Circonus - Circonus combines multiple monitoring, alerting, event processing, and analytics tools into one unified solution.

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.

Sawmill - Sawmill is a universal log analysis/reporting tool for almost any log including web, media, email, security, network and application logs.

Zabbix - Track, record, alert and visualize performance and availability of IT resources