Monitoring of CPU consumption is a very basic requirement in many areas of software. It is especially valuable in the frame of Internet applications, in support of specific aspects such as security, reliability and adaptability. This paper is set in the context of J-RAF2, a Java-based framework exploiting bytecode rewriting techniques in order to garantee the portability of CPU-managed applications. We briefly recall this implementation technique and present an example of CPU monitoring module to validate this new approach. Depending on the application, resource management may involve simple low-level accounting of CPU usage, or higher-level tools that collect accounting information from several sources in order to enforce sophisticated strategies. This paper shows that CPU monitoring modules may be easily built to work on top of classes rewritten with J-RAF2, and that they will be entirely portable across many kinds of Java deployment technologies (standalone applications, applets, servlets).