Loader.io - Loader.io is a simple cloud-based load testing service
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.
Loadium - Performance Testing & Load Testing Tool
AppDynamics - Get real-time insight from your apps using Application Performance Management—how they’re being used, how they’re performing, where they need help.
LoadFocus - Cloud Testing Infrastructure | Cloud Testing Services and Tools for Websites & APIs.
Zabbix - Track, record, alert and visualize performance and availability of IT resources