Re-implementing the game in JavaFX Mobile would only make for a tech demo, as NO device manufacturer or operator has announced support for JavaFX Mobile. Since NO real device exists to test on, the question whether it would need code signing is purely academic.
I would rather port to Android, as there are a couple of devices already out there (thats 2 more than JavaFX Mobile
), and there are many more in the pipeline from every major device manufacturer and operator. Unfortunately, Google hasn't implemented any bluetooth support for Java yet.
So, I'm sticking with J2ME for now. It's still the best platform for a hobby programmer, even if not for much longer.