Ghost Digital Cinema released a documentary about professional skateboarder Sean Malto that was shot entirely on an iPhone using an app called FiLMiC Pro, which is just $9.99 on the App Store. The filmmakers supplemented the iPhone with equipment like professional lenses, a gimbal and a drone, but the heart of the operation was an iPhone and a $10 app.
In addition to the documentary, Ghost Digital Cinema posted a behind the scenes video explaining how they made the Malto documentary. The amazing things that people make on their iPhones never never ceases to amaze me.