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.

Yeller - Yeller enables developers to track the errors their users hit in their application and fix them instantly.

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.

Firebase Crashlytics - The most powerful, yet lightest weight crash reporting solution for iOS and Android developers. | Crashlytics

BugSnag - Not all bugs are worth fixing. Prioritize and fix software bugs that matter while improving software stability with every release.