Jeremy - at this point you'd be better off emailing me or (even better) writing to the Hecl mailing list, rather than relying on my RSS feed to notify me of SO articles related to Hecl!
Yes, Hecl can run as an 'embedded' interpreter. For instance, you could write an entire app in Java and only use the interpreter for callbacks in response to events.
Since J2ME doesn't have Reflection, you have to write the glue between your methods and what's available to the interpreter. It's pretty easy, though: PutsCmd.java
To modify variables, once again, you'd have to provide some glue. It's not that hard though. There are ways to map back and forth between Hecl values and Java values.
In any case, I watch SO from time to time, but the mailing list or email would probably be a better place for more detailed questions.