There is something to be said for simplicity, especially when it comes to applications that leverage web APIs for mobile devices. Enter Sparrow, an application for the iPhone, that serves as a good example of how a few web APIs can be elegantly implemented for use on a mobile device.
For anyone looking to find accurate and up to date information on vehicles, be it potential car buyers or dealers, Kelly Blue Book provides all the relevant data on car models, features and selling prices. It's an online service with an extensive database of car value data and vehicle information that is based on trusted and official information. The Kelly Blue Book InfoDriver API makes this data available to be integrated with other websites and applications.