WmMonitor

What is wmMonitor used for? Can it be used to monitor a document on a broker?

Mow, please attempt to look for your answer in the webMethods documentation before posting questions here.
The webMethods product comes with documentation for every component…including webMethods Monitor.
Have a look at the doc MonitorUsersGuide.pdf in
<webmethods_install>\IntegrationServer\packages\WmMonitor\pub\doc