ServerPilot.io - Centralized hosting control panel for Wordpress and PHP web sites
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.
Ajenti - Web administration panel for servers and custom hardware
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Webmin - Webmin is a web-based interface for system administration for Unix.
Better Uptime - We call you when your website goes down