Some may remember Java Simon - that JAMon clone based on ns with monitors (Simons) organized in the tree hierarchy. This project is still maintained (may be witnessed by people submitting issues) and was recently released in version 3.0.0 with some polishing and new stuff on a horizon too.
While the core of the API is hardly changed since 2.x times, we decided to drop Java SE 5/6 schizophrenia and focus solely on technologies based on Java SE 6. JDBC3 driver is gone (JDBC4 is there), JMX is finally not the single module compiled with different JDK (because of JMX 1.4), etc. There is new stuff of course - mild Spring integration (aspect), simple web filter and simple experimental GWT console is in the development right now.
Oh, and I forgot - it's all on Maven central too!