I had Focos for iPhone on my list of future apps to review but Sam Byford beat me to it.
Focos has long been one of the most ambitious photo-editing apps on iOS, giving you control over the depth map generated by dual-camera iPhones in portrait mode. You can adjust aperture, simulate different styles of bokeh from various lenses, choose different points of focus, and so on.
Great app. Just get it. Depth of field to old photos makes good portraits.