Firebase Crashlytics - The most powerful, yet lightest weight crash reporting solution for iOS and Android developers. | Crashlytics
ServerSuit - ServerSuit is a browser based program that enables remote Linux administration, monitoring, website hosting, and server setup automation.
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.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Apptentive - Apptentive’s mobile customer engagement software helps companies listen to, engage with, and retain their customers.
AppZero - AppZero is a monitoring and migration tool that allows users to keep track of different applications and servers in both simple and complex IT environments.