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.
Exceptionless - Don't let your users walk away in frustration.
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.
Xamarin Insights - Xamarin Insights is a real-time app monitoring platform.
RootCause - Record, Replay and Reproduce JavaScript Errors
AirBrake - Airbrake is the leading exception reporting service, currently providing error tracking.