Don't know if anybody still reads this, but here's the menu system (filebrowser and all). Still need to do a posix port, and I had problems porting it to gp32 because of new/delete I think (I'd appreciate help with that), but I think most of it is there.
http://elektron.its.tudelft.nl/~brouwe25/hm/
http://elektron.its.tudelft.nl/~brouwe25/hm/