MachDB is machine database to catalog of the changing state of your hosts. It consists of a database, an aggregator, an XML spec, and some example information gathering scripts. Along with a Web UI, these form the basis of a system that will allow you to catalog the current and historical state of the hosts in your infrastructure. It has been designed with scale in mind, and the goal is to support 10k hosts. It is being actively developed and is used in production at a few organizations.
Sequencer is an engine used by system administrators for the computation and execution of sequences of actions over hardware or software. It can ping various devices in parallel, power on your whole cluster, or generate an Emergency PowerOff (EPO) script for your data center or cluster. It takes into account various dependencies (power off nodes before switches, clients before server), deals with failures kindly, and is very efficient (>4000 nodes in less than 10 minutes).