Apple announced the software development kit (SDK) for the iPhone today. While you won't be able to distribute or run your apps on an iPhone yet (that'll come in June), you can download a beta of the SDK today (if you can get to the site -- it's been a bit busy). The SDK is free to download and develop with, but distributing apps will require a $99 per year fee for Apple to host and market your goods. You decide the price, free or otherwise. The even bigger news for geo-minded people, though, is that Apple is opening up their programmatic interface with the "Locate Me" feature in Maps.app. Called Core Location, developers will be able to use a documented API to develop apps with location awareness.