OctoPerf - OctoPerf is a SaaS load testing solution, based on JMeter.
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.
StresStimulus - Load testing tool for websites and mobile that works with hard-to-test applications.
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.
SmartMeter.io - Performance Testing with Enterprise-Level Features with a familiar jMeter interface
Zabbix - Track, record, alert and visualize performance and availability of IT resources