You are correct that BPEL's support for endpoint reference manipulation is something that is done within a business process as part of its execution. This is typically to support dynamic addressing by extracting endpoints from messages or constructing them from some data within the exchange. I wouldn't try to modify your process definitions to have knowledge of your monitoring requirements. This should be external and if done properly then completely declarative.
If you're using Apache ODE within ServiceMix then you should be able to handle this with a Camel route. Have all of the endpoints for your process deployment target a small camel route where you can listen in or T the message or whatever behavior you're trying to monitor.
If you're using Apache ODE within a simple web container, then you can still bind the endpoints externally from the process to be the endpoint of your choosing. See their deployment descriptor documentation for more info.