Efexio is a free universal app (with many in-app purchase options) that lets you add professional visual effects to videos you shoot on your iPhone, iPod touch or iPad. The app comes with free dinosaur and dragon effects, and you can purchase more from within the app. The extra effects are US$1.99 each.
Efexio excels with the control of the effects. You can rotate them, change the lighting position, add haze, and even adjust the color cast to smoothly integrate the effects into your videos. The objects cast shadows, which makes them all the more realistic.
You can take a video from within the app, or use one you have already taken. Effects are easier to add if the camera is held very steady or on a tripod. Once a video is created, you can share it to YouTube, Facebook or email it. Movies are not rendered at full resolution; you can choose 640 x 360 or 960 x 540. The Pro Version of the various effects, a $9.99 upgrade for each (!), gives you high-resolution output.
The effects are from Tippett Studios. Phil Tippett is a special effects legend, and his work includes Jurassic Park, RoboCop and Matrix Revolutions.
Using the app was fairly straightforward, although I had to refer to the manual a couple of times. The icons for editing are not always intuitive, but once you use the app, the workflow is pretty easy to follow. Efexio provides video tutorials online.
I had a couple of crashes when loading an external video. The crashes didn't happen consistently, but frequently enough to be irritating.
The nearest competition to Efexio is Action Movie FX, also a free app with plenty of in-app purchase options. The app has similar features and also high-quality output. Both apps get excellent ratings from users. Efexio also plans to offer an OS X version of the app.
Efexio for iOS requires iOS 6.0 or greater, and is optimized for the iPhone 5.