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.
TypingDNA Authenticator - 2FA codes in your browser, secured by the way you type
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
PropelAuth - PropelAuth hosts and manages your authentication.
Better Uptime - We call you when your website goes down
Authorizer - Authorizer is an open-source authentication and authorization solution for your applications.