Load Impact - How many users can my web site handle?
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.
Check Point Quantum Security Gateway - Quantum is the next-generation VPN security gateway that delivers the core security benefits of a firewall, next-generation IPS, antivirus, and Web-filtering without sacrificing performance.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Signal Sciences - Signal Sciences is a software as a service platform providing security monitoring and defense for your web application.
Better Uptime - We call you when your website goes down