UpdraftPlus - UpdraftPlus is a WordPress backup plugin.
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.
Duplicator Pro - Duplicator Pro is a Wordpress migration and backup plugin.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
WPvivid Backup - Wordpress Developer
Better Uptime - We call you when your website goes down