Or two DS systems.
The support missions in particular are the greatest thing about it. You can give the player in the other game all kinds of helpful perks. You can give them 1.5 times the prize money (stacks with amulet coin), double experience (stacks with lucky egg), faster hatching (stacks with flame body), faster happiness growth and half off at all Pokemarts!
The two you are able to do for the other player are randomized, but they change around as you do the missions in the entree. The other missions are pretty stupid and boring, but they are easy. My favorite power is half off at all Pokemarts! Dusk Balls for 500 ftw!