I've seen your question in the Eeveelutions Challenge Thread ^^
I've used pokéSav to hack in my Eggs. It's a bit tricky, and it took me a while to make them look like actual Eggs fitting the Storyline, but I eventually got there.
I'm no master at using PokéSav and all, so what I did was start my game, obtain my PokéBalls, capture 6 random Pokémon, save, export the save file and then simply edit them into Eevee Eggs by choosing Eevee from the Pokémon list, checking the "Is Egg" button, choosing Run Away or Adaptability as an Ability (even tho I'm pretty sure they get randomly generated upon hatching anyways, but I just wanted to be on the safe side), picking a valid moveset and including the Egg moves I wanted, setting the Class to 2 since Eevee is a Pokémon that changed Ability upon evolution. Oh and I left the IVs untouched since they were the IVs of the Pokémon I caught, even if they were crappy. And don't forget to change the level to 1 and use the Stats Edit "All Max" button to set your stats acording to the IVs and level. You could also choose to make them Shiny but, again, I think that gets randomly generated upon hatching as well o.O I'm quite sure my natures and Abilities and stuff got randomly generated upon hatching in D/P/Pt. Set the PP left on your moves to 0 since that will most likely make them come in either at 0 PP or their default number and remember to set the Met at Level and Met at place to 0. And you can set the Egg Recieved At anywhere you want. I chose Twinleaf Town to stick to the backstory xD
Now, I don't know how to import save files into actual cartridges, but if you're playing on an emulator, just run the Emulator, open the game of your Choice, click on File> Import and pick your edited Save file and then press Ctrl+ R to refresh and there you have it xD luckily, on D/P/Pt, you don't need to mess around with Hex Values for Location and stuff so it's easier to get Eggs to look like you got them anywhere you want xD The tricky part is in HG/SS where you need to mess around with Hex Values and stuff >.<
Anyways, hope that helped.