Wal-Mart is jumping into the mobile payment game. Starting Tuesday in select stores, shoppers can now pay using Wal-Mart’s smartphone app.

Heavy hitters like Apple, Samsung and Google are already in the mobile payment space, so there’s plenty of hype around it. But it’s still new and not that many Americans are actually using it. With $482 billion in yearly sales, Wal-Mart is big enough to have serious impact on the mobile payment landscape. Right now, that space is not too well developed.

“One of the hardest things in payments in launching anything new is getting merchants and consumers on board at the same time and in enough density to get the new payment method geared up,” said Karen Webster, CEO of Market Platform Dynamics.

Wal-Mart certainly has density, but that doesn’t mean it’ll be easy.

“What they have to do, though, and what mobile payments has to do in general is move past the novelty phase and to the utility or ubiquity phase,” said Andy Schmidt, principal executive advisor with CEB TowerGroup.

He and others say that one way Wal-Mart could drive interest is offering coupons and loyalty points through its popular app.

Mobile payment rollouts are about more than payments. The idea is to use the app to lock in customers and keep them away from competitors. Customer captivity is one of the most powerful sources of competitive advantage.

Mobile pay is also another chance to learn more about customers, which Wal-Mart has been big on since long before big data was all the rage.