At the time of this writing, Apple is holding a press release to announce their API for the iPhone; you can check out the live feed here. They’ve announced a lot of really incredible stuff so far, but the part that I was most intrigued with is this:

We have a complete set of APIs for your app to talk directly to the contacts DB on the iPhone, and an entire database API with SQLite. … Core Location – we’ve taken that and patched it into an API so you can create location-aware applications. [emphasis added]

Imagine the possibilities this brings! Zillow can now make an app that shows information about all of the properties within a half-mile radius of your current location. IDX developers can create apps that show users properties for sale or open houses as they drive around a neighborhood. MLSs vendors can create locatation-aware comp programs to help agents impress sellers and pick up contracts. The list goes on. Yay!