WebGazer is an uptime monitoring platform that checks if your website is up as it should be and notifies you if anything goes wrong
Uptime Doctor - You can monitor up to 5 URLs with 1-minute monitoring interval, for FREE!
UptimeRobot - Free Website Uptime Monitoring
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.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
Pingometer - Pingometer is a service that monitors the uptime, downtime, and performance of websites. Get 24/7 monitoring - sign up for your FREE account today!