As you probably know, the movie Deja Vu features a gizmo that can display events from anywhere within a specific area exactly 4 1/2 days in the past.
I recall a story about a similar device which was supposed to be limited to centuries rather than days in the past. A scientist on the project discovers that there is no such limitation and breaks the news that the device can display images from any time in the past at any spatial location. What he doesn't realise is that this will destroy privacy: if you can see what e.g. your spouse was doing one nanosecond in the past, you can effectively spy on them in real time.
Anyone recognise it? I think it was by a pretty high-profile writer.
