How It WorksHorizon is an iPhone app that auto-magically ensures that your videos are shot in landscape mode. If you rotate your iPhone 45-degrees, the app simply adjusts the frame to maintain its aspect ratio. No matter how you’re actually holding your iPhone
You can record videos in 720p and Full HD. There's also an option to mirror videos to your Apple TV by using AirPlay.
If you always keep your iPhone horizontally when your're filming (as it should be), you don't need the app. But otherwise, definitely recommended!
The Horizon app is available for a limited time for $0.99. It costs normally $1.99. So, If you think you're going to use the app, be sure to grab it as soon as possible.