I've been making modern kilts, with slit pockets, thats my vote, I have tried the under apron pocket and cargo pockets, and I really do not like how either look or are used with the kilt.
These are pictures of the two I have made, I need to make them bigger but the two I have made are big enough for a cell phone or a money clip, which is all I really need when I am walking around in my kilt.