WebGazer is an uptime monitoring platform that checks if your website is up as it should be and notifies you if anything goes wrong
StatusPing - Monitor everything about your website
UptimeRobot - Free Website Uptime Monitoring
Oh Dear! - Website monitoring, without the hassle
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.
Hexowatch - Your AI sidekick to monitor any page for changes
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring