Thanks to Starry Might in our forums for bringing this up here.

From June 3 through the 13th, Australians can pick up their very own Jirachi from either Toys "R" Us or Big W. This Jirachi can be downloaded to any of the five 4th generation games, and if it's downloaded or traded to a HeartGold or SoulSilver game it will unlock the Night Sky's Edge route for the Pokéwalker on that game. The event has just started but it won't last long, so hurry up if you want one!