According to RPGamer, copies of Dragon Quest Monsters: Joker preordered from Amazon, GameCrazy or GameStop will include a "combination DS charm, keychain, and map." Apparently the map can also be used as a screen cleaner.
Alone, none of these are particularly unusual giveaways. The cloth map has been an RPG box standby since early Ultima, and keychains are ubiquitous as preorder bonuses. But in combination? Are we really supposed to hang our keys from our DS? We'll need more than a screen-cleaning map (that part, at least, is super-clever) to buff out the hundreds of scratches to the surface of the system.