Hexnode MDM - Mobile Device Management solution from Hexnode helps you monitor, manage and secure mobile devices across your organization.
UptimeRobot - Free Website Uptime Monitoring
Jamf Pro - Jamf Pro is comprehensive enterprise management software for the Apple platform, simplifying IT management for Mac, iPad, iPhone and Apple TV.
Uptime Kuma - A fancy self-hosted monitoring tool.
Scalefusion - Scalefusion is a Powerful Android, iOS, macOS & Windows 10 Device Management Solution for corporate-owned & employee-owned (BYOD) mobile, tablets, desktop & rugged devices.
OnlineOrNot - Uptime monitoring for software teams (even teams of one).