We're familiar with the concept of in-app purchases for digital content and upgrades, but how about in-app purchases of actual physical items? Amazon is pushing that angle with a new Mobile Associates API that lets you build links to goods sold through Amazon into your Android apps.
Developers earn up to 6 per cent of the selling price, drawing on the existing Associates model Amazon uses when sites to link to products sold through it. Amazon suggests three potential revenue models: selling individual items; promoting categories of items (which isn't much different to displaying in-game ads); or selling physical items paired with apps (such as the digital and physical versions of a board game in tandem).
It's potentially a less compelling monetisation strategy than pure in-app purchases, since you can't really link ownership of goods to specific app features. However, given that the overwhelming majority of app downloads are free, every little helps.
Announcing The Amazon Mobile Associates API [Amazon Developer Blog]