Upsilon is a distributed, flexible, and extensible system monitoring application. Being distributed means you run service checks on Upsilon nodes in your network where it makes sense, either on every server or on a management network, inside or outside the firewall. You can run checks on secure, hard to reach networks, and push those results to a central server. You can optionally execute "agentless" checks just by using SSH. Being flexible means that if you can script it, you can monitor it. Unlike most monitoring systems, the monitoring scripts are external to the main server, so you can use Upsilon to execute your monitoring scripts in an extremely robust way. Upsilon has been used to monitor many different things and is API-compatible with all nagios monitoring scripts. Being extensible means you can add monitoring checks to Upsilon at runtime without needing to restart the server. The upsilon-node and upsilon-web projects both have their own REST APIs.
Adagios is a Web-based Nagios configuration interface built to be simple and intuitive in design, exposing less of the clutter under the hood of Nagios. It has a REST interface for both status and configuration data as well a feature complete status interface that can be used as an alternative to the Nagios Web interface.
RealOpInsight is an advanced dashboard management toolkit for Nagios, Zabbix, Zenoss, Icinga, and other common open source monitoring systems including GroundWork, Centreon, Shinken, and op5 Monitor. It provides effective features for monitoring in demanding operations environments such as network operations centers and large data centers.
Shinken is an advanced monitoring system that is based on Nagios, but redesigned and rewritten from scratch while maintaining compatibility. It can monitor all IT devices from systems to end user applications. In case of a failure, Shinken can alert the operation engineers so they can promptly repair it. It has the same capabilities as Nagios along with more advanced built-in facilities such as load balanced and high availability monitoring.
DaVINCI is a dashboard builder and editor for Nagios systems. It can be used to add advanced visualization functionalities for Nagios-based management applications. Its editor uses a drag and drop interface to allow users get monitoring indicators and information directly from their databases and show them in a graphical and animated dashboard, without having to write a single line of code.
jmxtrans is effectively the missing connector between JMX and whatever logging or graphing package that you can dream up. jmxtrans is very powerful tool that reads JSON configuration files specifying servers/ports and JMX domains/attributes and then outputs the data in whatever format you want via special "Writer" objects that you can code up yourself. It does this with a very efficient engine design that will scale to querying literally thousands of machines. The core engine is pretty solid and writers are included for cacti/rrdtool, graphite, and stdout.
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.