Lemon targets Passbook with mobile wallet API

Apple’s Passbook (s aapl) has shined a light on the value of having one app serve as a container for cards, tickets and loyalty programs. That’s something Lemon went after first with its Smarter Wallet, which allows users to store a digital copy of receipts, IDs, payment, loyalty cards and insurance cards. Now Lemon is opening up its wallet to publishers, so they can directly integrate their cards and services instead of relying on consumers to do that.

LemonOn Wednesday Lemon is introducing Lemonade, a platform that lets publishers connect to Lemon through a new API. Previously, users had to take a picture of cards, coupons and receipts they wanted to store in the Lemon app. On a basic level, Lemonade will let companies connect their payment, membership and gift cards, coupons and tickets right into the Lemon app and will allow them to communicate with their consumers through the app. Lemon is offering a SmartCard Wizard, to help publishers easily build their own cards inside Lemon.

Lemon also wants developers to create add-on services that can provide additional value on top of the Lemon platform. Users will be able to browse a list of add-on services that offer discounts, offers and other services that interact with the data users store on their Lemon app. To help encourage development, Lemon is offering a $20,000 challenge for developers who create the best add-ons. There’s also a data dashboard for developers to see anonymous data on users, including demographics, spending habits and redemption rates for offers.

LemonOpening up to third-party publishers will pit Lemon against Passbook and perhaps Google’s larger vision for Google Wallet (s goog). Lemon founder and CEO Wences Casares told me Lemon will integrate with Passbook so users can send some cards over to Passbook.

But he believes Lemon will be a broader and more flexible tool for users, allowing them to not just call up information but manage their cards and communicate directly with providers through the app. He said publishers will be able to sell services through the app. For example, a credit card company could enable users to sign up for another card through the Lemon app. And unlike Passbook or Google Wallet, Lemon is available on Android, iOS and Windows Phone devices (s msft).

Lemon has more than 2 million users of its app, which is nice but much smaller than Apple’s addressable market with Passbook, which is in the hundreds of millions. It will be tough to convince some brands and publishers to connect to Lemon without a larger audience to justify the investment. But it shows how mobile wallet apps don’t have to be solely about payments. There is still a lot of room to compete to be an organizer of all the other stuff that goes into people’s wallets and purses.