I'm the creator of hierarchism (http://code.google.com/p/hierarchism/
I don't know much about leJOS honestly, but if you are interested in using my Java HSM implementation, I would be glad to help you get started.
It is not properly documented at this point, but I've been using it here and there with quite a bit of success, and also with a lot of ease.
HSM design complexity that you can achieve with this implementation is really high. The UML State Machine standard has been covered completely - at least afaik.
The state machine engine implementation itself is fairly lightweight, and (in my experience) high performing.
For your project, it may be important to note that hierarchism is tested and works fine on both Java ME and Java SE.
For starters, you can take a look at the Course/Enrollment test HSM in the source code, which can give you an idea of how to use the library.
So if you have interest, and have some questions, just let me know ...