Host Status Monitor App is a program that allows you to automatically monitor multiple Internet hosts for downtime. It runs from command line or GUI and can visually indicate host status or email you when a machine goes down. Configuration is performed through two files: a program configuration file (hoststatsmonitor.conf), and a list of hosts to be monitored (hostlist.txt).
Panoptes is a scalable, extensible network and host monitoring tool. It includes a dynamic Web management interface based on the Dojo toolkit. It monitors SNMP, TCP port availability, ICMP, HTTP response and content, and SSL certificates internally. It supports monitoring anything else via shell scripts. It also includes a packet capture tool for discovery of hosts, port, and OS.