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.
PreFlight - Preflight is an Automated Web Testing tool. Allows everyone to automate Web UI tests.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Firelab - Eliminate bugs with automated testing no-code required
Better Uptime - We call you when your website goes down
Monkop - Mobile testing cloud