Autodesk recently released an update to their 123D Catch photogrammetry app that now runs on the iPhone. Similar in function to the previously iPad-only app, a user captures a series of photographs that get forwarded to an online service for processing into a 3D model. This has to be one of the easiest ways of capturing 3D objects–just take a series of photos and upload to get a useable 3D object suitable for output on a 3D printer.