Multiple keyboards with different layouts

It is possible to do this in the xorg config:

Section "InputClass"
  Identifier     "Keyboard Catch All"
  MatchUSBID     "058f:9410"
  Option         "XkbOptions" "caps:super,terminate:ctrl_alt_bksp"
EndSection

Section "InputClass"
  Identifier "Apple Keyboards"
  MatchUSBID     "05ac:0236"
  Option         "XkbOptions" "altwin:swap_lalt_lwin,caps:super"
EndSection

However, GDM has its own way of managing you keyboard settings that will overwrite these xorg settings. I have not found a solution that works well with GDM.