What are some alternatives?
Angular.io - Angular is a JavaScript web framework for creating single-page web applications. The code is free to use and available as open source. It is further maintained and heavily used by Google and by lots of other developers around the world.
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.
ember.js - A JavaScript framework for creating ambitious web apps
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
React - A JavaScript library for building user interfaces
LogicMonitor - LogicMonitor is the SaaS performance monitoring platform for the world's best IT teams. Deploy Fast, Monitor More, Improve Ops.