I have started yet another open-source project: Too-OneBee. It’s both an embeddable and standalone web console for monitoring a J2EE application. It lives at Google Code: http://code.google.com/p/too-onebee/
It embeds a javax.scripting console for running scripts within the webapp, a JMX browser, a session/request/application/server context viewer, a JNDI browser.
I would like to add pluggable handlers so that, for example, one could add Spring integration, a JDBC tool (a la phpMyAdmin), etc.