Uptime Infrastructure Monitor - Unify IT Performance Monitoring and Optimization
Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Web Optimizer - IT Management
UptimeRobot - Free Website Uptime Monitoring
BeAnywhere Support Express - Get Live From the Cloud
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.