Best tools to monitor Tomcat
javasimon - Google Code Java Simon is a simple monitoring API that allows you to follow and better understand your application. Monitors (familiarly called Simons) are placed directly into your code and you can choose whether you want to count something or measure time/duration. News October 12th, 2012 - version 3.3.0 released - mostly (harmless) fixes From now on we are releasing under New BSD License leaving GPL behind.
JAMon - Documentation
MessAdmin - Notification system and Session administration for J