If you're shooting with action cameras, especially the GoPro HERO then you should take a look at these quick and easy FCPX plugins. They can correct the distortion from ultra wide views, and straighten up the horizon. It's not just for small action cameras, as I use the De-Fish plugin religiously whenever I'm shooting 4K with my Rokinon 7.5mm Fisheye lens on the GH4.
I highly recommend this set of plugins to speed up your workflow when working to de-fish fisheye lenses, or to remove that unwanted distortion from many of the Action cameras. I use my GoPro quite a bit on little gimbal stabilizers, and this is the best and fastest way to de-fish those images. Even faster than GoPro's Cineform software. Simply drag the plugin on to your video clip, and adjust your settings with sliders. Incredibly simple and fast and you can see the results immediately.
Action Cam Essentials is a powerful and vital plugin for anyone editing with action camera footage in Final Cut Pro X.
Features included with Action Cam Essentials:
Fisheye Removal: both automatic and manual modes for precise adjustment and removal of fisheye distortion caused by any wide angle lens.
Dynamic Stretching: stretch 4x3 aspect ratio footage to fit a 16x9 project without distorting your subject. This allows you to shoot using your camera's entire sensor and capture the maximum field of view (FOV) vertically and horizontally.
Color Grading Presets: over 20 professional color grading presets designed for use with the most popular brands of action cameras.
Letterboxing: achieve the widescreen look and reframe your shots by quickly and easily adding letterbox bars to your videos.
Title Layer Plugin: the plugin has been created in Final Cut Pro's title template framework to allow it to be easily applied to multiple clips at once.