Life hacks make tedious tasks like slicing avocados or opening jars a bit easier. Such tricks are for amateurs. Hardcore hackers slice open their arms, or hands, or ears to install magnets, RFID tags, and other nifty devices that open doors, transmit data to a smartphone, and do other cool, if somewhat pointless, things.

Photographer Hannes Wiedemann explores the wild world of DIY cyborgs in Grinders. The photos filling his book are not for the squeamish, as they present, in occasionally gruesome detail, the lengths these folks go to so they might live in the future. “They’re into technology, so they try to take shortcuts through technology," he says.

Look hard enough and you'll find 5,000 or so "grinders" in the US. The movement started in 1998, when Reading University cybernetics professor Kevin Warwick implanted an RFID tag in his arm so he could turn on lights with a finger snap. The subculture experienced explosive growth during the past five years as companies like Dangerous Things and Grindhouse Wetware offered a growing number of gadgets that let you feel electromagnetic fields or unlock your car without keys. To quote the popular online forum Biohack.me, grinders are here to "improve the human condition."

Wiedemann discovered this subculture through a friend in Berlin, where he lives, and found himself immediately intrigued. He spent seven months exploring Biohack.me, where grinders discuss things like the risks of nickel-coated magnets and engage in other unusual activities, like, say, giving away Madagascar hissing roaches (“Not for killing, or harming or experimentation,” the owner says. “Just pets.”). Wiedemann attended a cyborg fair in Düsseldorf, Germany, and spent six weeks in the US hanging out with people like Grindhouse Wetware co-founder Tim Cannon and Dangerous Things owner Amal Graafstra.

The highlight was Grindfest, a three-day shindig in the small town of Tehachapi, California. Some 50 grinders from all over the country crowded into the garage-turned-laboratory of Jeffrey Tibbetts, medical officer for the biohacking group Science for the Masses. The unusual gang of nurses, scientists, and IT professionals brainstormed ideas, barbecued, and hopped into Tibbetts's examination chair for new flair.

The photographer's witnessed more than 30 procedures throughout the project. The grossest? "The north star," in Düsseldorf, a quarter-sized disc with blinking LEDs inserted into a deep cut in the forearm or hand in. Why? "I wanna glow," a grinder replied.

Wiedeman's blinding flash illuminates the goriest details—a combination of metal, flesh, and blood that would make anyone squeamish. It might look medieval, but grinders aren't the only ones who believe implants are the future. Devices have been used to treat things like epilepsy and Parkinson's disease, and Elon Musk recently invested in a company building brain implants that link humans and software. If body hacks are the future, you might need a stronger stomach.

Grinders is available as a photo book.