Digital Photography Review reports: [edited]
The DxO ONE connects to your iPhone via a Lightning adapter. Weighing 108g 67mm tall, 48mm wide x 25mm deep, the DxO ONE is small enough to fit in your pocket, yet features a 1"-type BSI-CMOS sensor. That means great low light sensitivity due to the BSI design, and fantastic Raw dynamic range. Combined with the bright F1.8 lens, you'll get far better image quality than your iPhone's camera, with better low light performance and control over depth-of-field.
DxO is a leader in digital image-processing. The SuperRAW feature captures four Raw images in rapid succession, then combines these images in the desktop software using spatial and temporal noise reduction algorithms to generate a high quality, lower noise image. Simple image averaging of four images should lead to a 2 EV increase in noise performance due to shot noise considerations alone which, by itself, is impressive. But there's even more going on.
If there's any subject movement, the algorithm takes the sharpest representation of that subject. Furthermore, the quartet of shots are carefully analysed for motion blur to attempt some de-blurring of the image, which simulates image stabilisation.
Connect the camera to your iPhone, and you're instantly taken to the App store to download the camera app. A couple of steps later, and you're on to taking your first photo. After your app is already installed, connecting the ONE to your iPhone launches the app.