even better (finds submodules on its own):

cd ee
tar cfj footprints.tar.bz2 \
  ` git ls-files '*.mod' '*.kicad_mod'
   git ls-files '*.fpd' | sed 's/\.fpd/.mod/'
   git submodule foreach -q 'git ls-files "*.fpd" |
     sed "s|^|$path/|;s/\.fpd/.mod/"'`