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.

LogTailApp - LogTail is a local and remote (SSH) log file viewer and monitoring application for Mac OS X. It is a pure, modern, document-based Cocoa App

AppSignal - We monitor the software that makes your customers happy.

Hawk - Hawk provides visual user tracking and error reporting with live screen view, deep filtering and robust access control.

PreFlight - Preflight is an Automated Web Testing tool. Allows everyone to automate Web UI tests.

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.