We're all intimately familiar with the cameras on our smart phones, and we like to philosophize about the security cameras peeping at us from street lamps, but we sometimes forget that cameras quite literally surround us. From the sensors that see you're finished taking a piss and flush the toilet for you, to the ones that politely open sliding glass doors—" Thank you, door!"—we're constantly being watched.
This is hypnotically illustrated by a device created by Steve Mann, a electrical and computer engineering professor at the University of Toronto (whose much-ridiculed computerized eyewear predated Google Glass by a good 35 years and once lead to a bizarre encounter in a Parisian McDonald's).
The horribly-named veilluminescence is a light wand that illuminates as it's being watched, detecting and displaying a camera's field of vision.
Aside from being cool, Steve proposes that the device could be useful as well, either "by a user or owner of a surveillance system to visualize the efficacy of their own cameras" or "as a video 'bug sweeper' which uses video feedback to detect hidden video surveillance."
If you want to explore more of the science behind how it works, Steve wrote a detailed paper on the technology. The rest of us can just marvel at the horrifying beauty of the lines of sight of the cameras that surround us:
Okay, these last two aren't gifs, but they illustrate the cameras that watch you use the bathroom, which is pretty cool/creepy: