Thanos.io - Open source, highly available Prometheus setup with long term storage capabilities.
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.
InsightCat - Full-stack monitoring platform for your software and hardware. InsightCat is a cloud-based and AI-powered solution to enhance your system health estate through infrastructure monitoring and alerting capabilities.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
NinjaOne - NinjaOne (Formerly NinjaRMM) provides remote monitoring and management software that combines powerful functionality with a fast, modern UI. Easily remediate IT issues, automate common tasks, and support end-users with powerful IT management tools.
Better Uptime - We call you when your website goes down