3D scanning is useful for augmented reality gaming and 3D printing. There are plenty of expensive scanners on the market. MobileFusion is a research project focusing on turning smartphones into 3D scanners. It lets you create high quality 3D images in real time. This system does not need any extra hardware or an Internet connection to work.
The scans are good enough for 3D printing. You will be able to preview your 3D model to make sure you have scanned the object properly. The above video covers how this technology works. More information is available here.