Mobile commerce is a huge business opportunity because, at least in the United States, there is not much infrastructure to support it. That's why mobile platform company Appcelerator recently announced its integration with the PayPal API. Now iPhone, Android and iPad developers using the paid version of the company's Titanium framework also get the ability to conduct mobile commerce.
Zillow has released an application for iPhone users that builds on their Zillow API, the Microsoft Virtual Earth API and the iPhone's GPS capabilities. The Zillow iPhone app detects your location and shows data about nearby homes, including market values, photos, and which ones are for sale. It's a great example of a mobile mashup application that uses multiple APIs in meaningful location-aware context.