We pass under surveillance cameras every day, appearing on perhaps hundreds of minutes of film. We rarely notice them. London-based artist James Bridle would like to remind us.

Bridle has created a wearable device he calls the “surveillance spaulder.” Inspired by the original spaulder—a piece of medieval plate armor that protected “the wearer from unexpected and unseen blows from above”—the surveillance spaulder alerts the wearer to similarly unseen, if electronic, attacks. Whenever its sensor detects the the type of infrared lighting commonly used with surveillance cameras, it sends an electric signal to two “transcutaneous electrical nerve stimulation” pads, which causes the wearer to twitch.

That is: Whenever the spaulder detects a security camera, it makes your shoulder jump a little. You can see the spaulder in action in the video above.

The surveillance spaulder isn’t the only project that explains how hard-to-see surveillance might be countered. In October, a Dutch artist claimed to invent a shirt that confused facial-recognition algorithms; before that, the American designer Adam Harvey explored make-up, hair-dos and shawls that could confuse the facial- or body-recognition software used in drones. And many of these ideas hail back to science fiction writer William Gibson’s “ugly t-shirt,” a theoretical garment so hideous that surveillance cameras couldn’t stand to look at it.

But Bridle’s spaulder has a slightly different goal. Instead of obstructing cameras and algorithms, it merely alerts the wearer to their presence. It’s a technology—and an art project—of reminding. The surveillance spaulder provides a “a tap on the shoulder,” Bridle writes, “every time one comes under the gaze of power.”

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