WebGazer is an uptime monitoring platform that checks if your website is up as it should be and notifies you if anything goes wrong
Visualping - Visualping is the easiest to use website checker, webpage change monitoring, website change detector and website change alert software of the web. Read more about Visualping.
UptimeRobot - Free Website Uptime Monitoring
Distill Web Monitor - Distill is a web monitoring tool. It can monitor RSS feeds, a webpage or a part of webpage. Alerts in the form of pop-up, audio or emails can be received.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Monitoro - Monitor webpages and get fresh data sent to your webhooks.
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.