These are binary map files for displaying street maps on an Android device. See http://download.mapsforge.org/ for example files. The current parser only supports file version 3 (which is the latest version).
Kuang-che Wu, sorry but it's unlikely that I'll work on this in the near future. Hachoir3 doesn't work neither at home (with Python 3.2) nor at work (with Python 2.6), so I couldn't really test it, much less make actual use of it :-)