Rollbar - Rollbar collects errors that happen in your application, notifies you, and analyzes them so you can debug and fix them. Ruby, Python, PHP, Node.js, JavaScript, and Flash libraries available.
Fluentd - Fluentd is a cross platform open source data collection solution originally developed at Treasure Data.
Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.
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.
Logify - It is a real-time application monitoring and automated exception reporting.
Splunk - Splunk's operational intelligence platform helps unearth intelligent insights from machine data.