I am pretty sure I read on this forum (or was it in JIRA?) that full audit trial capability is planned for a future release. I think many of us are anxiously awaiting it.
Depending on what you want to audit, you could e.g. use AOP and intercept all calls to the database as your audit trial. Might not be that easy to do, but very complete.
What I have done in the past, is configure a <history-sessions> in the jbpm.cfg.xml file, a Java class that implements HistorySession. This way you can intercept anything that will result in a history record update. Admittedly, you still have to do a bit of coding (notably for checking the type of HistoryEvent and then acting accordingly), but it covers quite a bit in just one listener. Sadly this is not in the API docs, so you need to do a bit of digging in the code. There are 16 classes in the package org.jbpm.pvm.internal.history.events that each represents something you can capture.