Actually, the Korean made MMO "Ragnarok Online" by Gravity came out with a few Cell Phone games that gave you in game items and gold based on your performance in the Cell Phone games. It was pretty interesting. They had the "Kafra Quest" (Kafra Corp being the organization of Maid Outfit wearing NPC's that stored your gear and sold Teleports and other such things) where you were a Kafra agent and you went around and killed monsters and collected lost things. Then they made Class based games that were similar: Mage, Merchant, Acolyte, etc etc. I think a few of the cell games got ported to other territories than Japan and S.Korea, and 2 came to the US for a short bit on only one carrier and a limited amount of phone types.

It was a very nifty idea on a way to extend the influence and charm of the game to places where you couldn't always have a PC available.