Zabbix - Track, record, alert and visualize performance and availability of IT resources
Serilog - Backend Development and Utilities
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.
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
Prometheus - An open-source systems monitoring and alerting toolkit.
Logmatic - Logmatic is a log centralization, analytics & visualization platform to improve software & business performance.