What are some alternatives?
When comparing Eyes Of Network and Check_MK, you can also consider the following products
DiamanteDesk - DiamanteDesk is an open-source easy-to-use help-desk solution.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
openITCOCKPIT - openITCOCKPIT is an open source out of the box monitoring framework. It can be installed on Debian based distributions through apt and provides a user friendly web interface where you can create all your hosts and services you like to monitor.
Site24x7 - Site24x7 offers both free & paid website monitoring services. Monitor websites remotely and receive instant email/sms alerts if your website becomes unavailable. View uptime & performance graphs of your website monitors.
Spiceworks Help Desk - Help desk software features that work for IT
LogicMonitor - LogicMonitor is the SaaS performance monitoring platform for the world's best IT teams. Deploy Fast, Monitor More, Improve Ops.