jamon doesn't do what you are asking.
JAMon does allow you to monitor several different aspects of your code with no code changes:
1) Using jamon
jdbc driver you can track sql stats, jdbc method call stats and jdbc exceptions
2) Using the jamon
servlet filter you can track page hits, as well as performance of your pages
3) Using the jamon log4j Appender you can see how many calls you make to debug/info/warn/error/fatal as well as when they were last called and in addition the messages written to them can be viewed from the jamon war.
4) Any interface can be monitored via the jamon interface monitor with one line of code. For example
MyInterface my=(MyInterface) MonProxyFactory.monitor(new MyImplementation());
my.methodCall(); // any interface methods will be monitored for performance and excetpions
5) Using jamon in conjunction with AOP you can monitor any method pretty easily.