Researchers at UC Berkeley have successfully used functional Magnetic Resonance Imaging (fMRI) to reconstruct what people see. The video below shows what the test subject viewed on the left and what the researchers reconstructed on the right. Some of the images are very close to what the viewer actually viewed. The video quality at which they can reproduce the brain's activity is still not very good, but one day in the future you may be able to use the most powerful sensor of all to take your pictures....your brain.
More details about the study