An ordinary digital picture frame cycles from one picture to the next on a timer.
The Weeping Angel digital picture frame incorporates a small camera, and a computer chip smart enough to determine how many people are looking at it at any given time.
Whenever the number of people looking at the picture frame becomes zero, the picture is cycled to the next one.
Naturally, the device comes preloaded with images of the Weeping Angels from Dr. Who.-- goldbb, Jun 29 2017 The Mezzotint http://www.thin-ghost.org/items/show/145Prior Art ... [8th of 7, Jul 02 2017] The Dark Mirror http://weekinweird....ror-haunted-object/The above link reminded me of this [notexactly, Jul 05 2017] This reminds me of a related idea I've had for a while but never thought to put it on my list of things to halfbake because I was initially considering it as an idea to fullbake, but that's now out of the question. So thanks. Maybe I'll get around to posting it soon. I've noted down your idea as prior art.-- notexactly, Jun 29 2017 Fullbaking is hard.-- 2 fries shy of a happy meal, Jun 29 2017 Gaze detection is used for some smartphone applications (e.g., pausing a video when the viewer looks away). Should be a simple matter to write a variation to do this.-- tatterdemalion, Jun 30 2017 8/7, Nowadays, "sympathetic ink" is a bit hard to come by, and we must make do with technology.-- goldbb, Jul 08 2017 random, halfbakery