Crisp Status Page - Monitor servers and let users know if something goes down.
UptimeRobot - Free Website Uptime Monitoring
ContainIQ - Kubernetes native monitoring instantly
Uptime Kuma - A fancy self-hosted monitoring tool.
Robusta - SRE Copilot for Kubernetes
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.