iOS: Apple recently introduced a new Portrait Mode that adds a faux depth-of-field effect when you take a photo, but it only works on the iPhone 7 Plus. With Patch, you can get a similar effect on any iPhone.
Patch utilises neural networks to analyse your photo and determine the subject matter. It's far from perfect, so this is more of a fun photo toy than a serious tool. But the developer anticipated that it won't always accurately find the outline of your intended subject, so you can adjust the mask yourself by manually highlighting or erasing the affected areas of the blur. It will work most effectively when you take a clear picture of someone from the waist up. The above examples were taken under ideal conditions and look great.
But here are some random examples that I did with just random images on my phone:
It struggled with the toddler in the center, but did pretty well with the image of me on the left. On the right, you can see the editing tool to adjust the mask.
Patch is free, but it will add a small watermark to every photo. It costs $US1 ($1) without the watermark.
Patch [iTunes App Store]