Google has added a new 'Lens Blur' feature to the stock Android app that allows you blur an image after it's taken.
Many will see this lens blur effect in professional DSLR photos, where a part of an image is in focus while the background or foreground are out of focus. This is also sometimes called 'Bokeh'. Usually this effect requires a large sensor and a lens which can let in a lot of light.
Lens Blur on the Android camera app will allow you to have this bokeh effect artificially. It can measure the depth of an image and then simulate the effect when you want to apply it to the image. You can even change how much blur you would like.