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.
Facebook Safety Check - Connect with friends and loved ones during a disaster
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Crisis Response on Facebook - Find more information about crises and crisis response tools
Better Uptime - We call you when your website goes down
RscMe - Rescue & Emergency app for Apple Watch