Wondering whats the difference between Google Wallet Billing APIs and Google Play in-app billing. Whats the advantage of using GooglePlay in-app purchase billing service over Google Wallet billing APIs? I see Wallet APIs also supports Android, then whats the point in using Goole Play IAP app? I'm at a point to implement a cross-platform solution for digital goods purchase in app. My question is what Wallet APIs don't offer over Google Play IAP service?
There are several Google Wallet APIs and they have different applicability. The following may help you.
Google Play In-App-Billing - Used for any digital goods purchase from native Android Apps. http://developer.android.com/google/play/billing/index.html
Google Wallet Digital Goods API - Used for any digital goods purchase from Web Apps. https://developers.google.com/commerce/wallet/digital/
Google Wallet Instant Buy API for Web - Used for physical or digital goods purchase from Web Apps - but you need to have your own payment processing. Google gives you a proxy card to charge. https://developers.google.com/commerce/wallet/instant-buy/web/tutorial
Google Wallet Instant Buy API for Android - Used only for physical goods or services purchase from native Android apps - you need to have your own payment processing. Google gives you a proxy card to charge. https://developers.google.com/commerce/wallet/instant-buy/android/tutorial
For 3 and 4 you need to fill out an interest form to get access. http://getinstantbuy.withgoogle.com/
Hope this helps.
One important difference comes in the form of handling refunds.
Google wallet can be used to fund refunds, but may not handle requests for refunds. Whereas in app billing would forward you a request for refund.
I can see that being an issue when dealing with large volumes of purchases.
Source -http://developer.android.com/google/play/billing/billing_admin.html
来源：https://stackoverflow.com/questions/19525166/google-wallet-for-digital-goods-api-vs-google-play-in-app-billing