Same thing happens in the emulator, btw.  I've been poking around a bit more, and it seems to me that the physics doesn't get updated.  If I call the world.step(dt, iter) method manually, in the draw method, then the box starts jumping around, but the updates aren't done nicely, the physics don't get updated smoothly.  

As an update, the bowrap2d just doesn't seem to work on my phone or emulator.  However, fisica http://www.ricardmarxer.com/fisica/ works just fine, for a few simple examples that I tested it with.

Fisica works perfectly for me too on galaxy spica android 2.1 / processing 0914

There's something odd about fisica though.  Or maybe it's normal, I don't know.  Here's the experiment.  I setup a bunch of "bins" using rectangles that were very thin (a few pixels) but long from top to bottom.  Then I dropped boxes or circles in each bin.  The boxes and circles were a few pixels narrower than the distance between two rectangles (walls).  The odd thing is that after some bouncing, the boxes or circles went through the "walls", i.e. through the rectangles, migrating to the neighboring bin.  I was under the impression that objects don't go through each other.  

Thanks Ricard, Fisica.setScale() fixed the problem with objects going through each other!

Thanks for the above, it was helpful as I'm facing the same problem.