This is billed as pure tech, but its use in tracking material, possibly copyrighted material, are obvious: TinEye, a reverse-image search.

The idea is that you upload a picture to it and it tells you where else on the Web it has seen that picture. One obvious use would be sourcing material - I have this picture, who might it have come from - and another would be finding people who are using your images. Imagine a widget that would let you feed a full Flickr stream or Picasa album to it, rather than trying to upload one image at a time...