PhotoRaw for iOS is a viewer and developer for image files in raw format. Raw file formats from most camera manufacturers are supported, for example Nikon NEF files, Canon CR2 files, Leica DNG files, etc – see the product web site for a full list of supported cameras. PhotoRaw allows you to view these files at full 1:1 pixel resolution, even 16 mega-pixel plus images such as from a Nikon D3x or a Leica M9.
This great app has just been updated with support for the Leica M Monochrom. There’s also a bug fix that resulted in some Canon sRaw format images not importing correctly.