Unity has announced that it's making its mobile game development tools free to use for most independent and small studios. Unity has always been a popular engine both for mobile game development and for cross-platform game creation, but up until now, you had to pay about $800 to actually publish Unity-created apps on the iOS or Android stores. Those basic add-ons have now been made free, so anyone can now download Unity, and then use it to publish an app for iOS or Android without paying a fee for the engine.
Unity still has pro versions available for sale to both iOS and Android developers, and anyone making over $100,000 per year with their releases is required by Unity to go ahead and purchase a pro license. So there are still some limits on exactly how this all works, and if your iPhone app does hit it big, Unity still would like its due. But starting off for free should open the door for even more indie devs to get in and try Unity, and make for even more and better games on the App Store.