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.
Flamelink.io - Flamelink.io is a headless CMS for Firebase.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
PushTable - Headless CMS for Google Firestore and Firebase
Better Uptime - We call you when your website goes down
Strapi - Strapi is the most advanced Node.