https://www.rochester.edu/communications/resources/web-seo/wordpress-theme/site-alert/
Site Alert - University Marketing and Communications
site alertuniversity marketingcommunications
https://pingability.com/
Pingability.com: Web Site Monitoring and Alert Service
Pingability is a server and website monitoring and alert service. It monitors your server or website and alerts you when it goes down.
monitoring and alertweb sitepingabilityservice