Very Simple Network Monitor is a bash shell script CGI that monitors a number of services on a network. It currently checks for node-up, TCP service up, and UDP service up. A service or system can be put in maintenance status to avoid repetitive alarms. It is easy to customize, trigger alarms by email, or whatever you like (depends on nmap for TCP/UDP service checks). Installation is also simple. It generates HTML with all statuses, and for all services just in one view.