Focus after taking the photo: Computational Photography

Here's a novel idea, take your photo and then decide where you want the focus point to be! This is one of the possibilities of computational photography, it is unclear from this article if it is possible without a plenoptic camera (uses microlenses to capture multiple images). I wonder if this can be used to extend the DOF as well as just choose your focus point. Oh and it has possibilities for various other uses such as HDR which combine multiple images.
Photo Rumors: Startup company Lytro promises to redefine photography with computational imaging