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.
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.
UptimeRobot - Free Website Uptime Monitoring
Atera - Atera’s all-in-one platform enables IT professionals to gain access, visibility, and control over all their networks and devices from anywhere, so they can work smarter and light years faster.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Microsoft Operations Management Suite - Microsoft Operations Management Suite enables user to gain visibility and control across the hybrid cloud with simplified operations management and security