NewRelic - New Relic is a Software Analytics company that makes sense of billions of metrics across millions of apps. We help the people who build modern software understand the stories their data is trying to tell them.
NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.
Dynatrace Ruxit - All-in-One Application Performance Monitoring
mackerel.io - mackerel.io is a server and application performance monitoring platform.
DareBoost - DareBoost is an online tool to test, analyze and monitor your website: speed, SEO, quality, security. All you need for website optimization in a single service.
BizTalk360 - BizTalk360 is a web based production support/monitoring tool for Microsoft BizTalk Server.