Netdata collects metrics per second and presents them in beautiful low-latency dashboards. It is designed to run on all of your physical and virtual servers, cloud deployments, Kubernetes clusters, and edge/IoT devices, to monitor your systems, containers, and applications.

An advanced network monitoring solution to monitor network up/downtime, traffic and usage. Features include availability, performance, and bandwidth monitoring (SNMP, WMI, packet sniffing, NetFlow), instant alerts, reporting, failover clustering.

Cabot is a free, open-source, self-hosted infrastructure monitoring platform that provides some of the best features of PagerDuty, Server Density, Pingdom and Nagios without their cost and complexity.

PHP Server Monitor is a script that checks whether your websites and servers are up and running. It comes with a web based user interface where you can manage your services and websites, and you can manage users for each server with a mobile number and email address.

Netweak is a delightful, minimalist monitoring platform that gives you insights on performance and availability for your linux servers & websites.

Enterprise-ready monitoring solution that provides unparalleled flexibility for IT to address both immediate and unforeseen operational issues, including infrastructure and IT processes.

Monitis is a Cloud monitoring and IT analytics service offering Website Monitoring, Server Monitoring, Network Monitoring, Application Monitoring, Cloud Monitoring, and Custom Monitoring.

Proactively monitor your websites and online services. Receive immediate notification when a problem is detected so you can quickly resolve the root cause and prevent potential escalation.

CloudMonix provides advanced cloud monitoring and automation for applications and services deployed on the Microsoft Azure and AWS platforms and built with MSPs, CSPs and DevOps in mind.