Source: http://gizmodo.com/5995231/focustwist-the-closest-to-a-lytro-camera-your-iphone-can-get
While we'll still have to wait a bit for Lytro powers to come to our smartphones on a hardware level, we can at least approximate the neat little camera's refocusing powers with what we've already got. And this is where FocusTwist for iOS steps in.
Lytro employs light-field technology when it takes a photo, basically absorbing every possible ray of light and merging the images together, letting you refocus the photo anywhere you want. FocusTwist uses a similar idea: take a photo within the app, hold still for a few seconds while FocusTwist goes to work snapping multiple images with differing focal planes, and come away with a photo that you can readjust as you please.
Because FocusTwist has to work with iPhone's camera, the results obviously won't be as drastic as they would with a Lytro. But if you frame your pictures carefully (the app works best when you frame your shot with a very close object in front and a larger subject off in the distance), you'll likely have a blast Twisting and refocusing to your heart's content. So while this won't be too useful for quick shooting at a moment's notice, if you're looking for a neat little trick that makes use of the camera you already have, the $2 you'll be shelling out is definitely cheaper than buying a Lytro.
The Best
iPhone-cum-Lytro
The Worst
Framing shots just right