Imagine for a moment that you could choose any superpower you wanted. If you’re the demonstrative sort, you might be tempted by something dramatic, such as Hulk-like strength or the ability to fly. Or perhaps you’d prefer something a little more discreet, like a self-healing body or the power to read minds.

But if you’re a certain type of pragmatist, you’ll dismiss all of the above as a mere parlor game. Why waste time dreaming about things that are impossible (for now, at least) when you can have a more modest superpower today, at a reasonable price?

That’s the premise behind a small but growing subculture of DIY biohackers, body hackers, grinders, and self-made cyborgs, who are taking advantage of widely available technologies such as tracking chips, LEDs, magnets, and motion sensors to imbue themselves with a sixth sense of sorts. They range from professionals such as Kevin Warwick, the publicity-friendly Reading University professor behind Project Cyborg, to spiky-haired cyberpunks such as Lepht Anonym, whose taste in surgical tools runs to vegetable peelers. Call them “practical transhumanists”—people who would rather become cyborgs right now than pontificate about the hypothetical far-off future.

So what kind of sixth sense could you acquire today if you were in the market? Anything from infrared vision to an internal compass to a sort of “spidey sense” that alerts you when something is approaching from behind. And the cost can run from the tens of thousands of dollars to as little as a few bucks, as long as you have a scalpel and a hearty tolerance for risk and pain.

The concept of implanting bionic devices is by no means radical or new in the medical field—just ask anyone with a pacemaker or an insulin pump. But the notion of healthy people sticking gadgets in their bodies for fun, profit, or sensory augmentation is a more recent phenomenon. It’s an offshoot of the transhumanist movement, which took root in California in the 1980s among a set of philosophers, dreamers, and technophiles who believed that emerging technologies could reshape humanity for the better. But while the transhumanists held conferences, wrote books, formed think tanks, and sparred with bioethicists, a few who shared their vision began to wonder where the action was.

In 1998, Warwick, a professor of cybernetics, had a doctor surgically implant a simple radio-frequency identification transmitter in his upper left arm, in an experiment that he called Project Cyborg. The chip didn’t do a whole lot—it mainly just tracked him around the halls of the university and turned on the lights to his lab when he walked in. But Warwick was thrilled and the media were enchanted, declaring him the world’s first cyborg. (Others bestow the title on Steve Mann of the University of Toronto, who has been wearing computers and cameras on his head for decades.) He later followed up with more complex implants, including a 100-electrode chip that transmitted signals from his wrist to a computer.

Warwick’s initial RFID implant was a turning point in the history of transhumanism not because it represented a great technological leap, but because it required no technological leap at all. What he did, anyone could do. To some, that made him a charlatan. To others, it makes him a hero.

What it undeniably did was pave the way for people with far fewer resources to experiment with enhancements of their own—often without the aid of medical professionals. One of the most extreme examples is Anonym, a tattooed young woman from Scotland who describes herself as a “scrapheap transhumanist.” In a memorable appearance at a conference in Berlin in December 2010, Anonym described her first foray into grinding thusly: “I sat down in my kitchen with a vegetable peeler, I shit you not, and I decided to put things in my hands. … The first time I ever sat down, it went horribly, horribly wrong. The whole thing went septic, and I put myself in the hospital for two weeks.” For most people, that would be ample motivation to swear off grinding for good. But Anonym learned lessons and kept at it, successfully implanting an RFID chip before moving on to other implants like a temperature sensor and a neodymium magnet that would vibrate in response to alternating current. Her exploits, in turn, inspired others.

For Tim Cannon, a mild-mannered 33-year-old software developer from Pittsburgh, it was the magnet idea that touched a nerve. “I’ve been a science fiction fan since I was a kid,” he told me. “I’ve just always been interested in nerdy kind of stuff.” When Cannon first saw Anonym, his first thought was, ‘Oh no, the revolution started without me!’ ” Within a month, he had enlisted a professional tattoo artist to install a polymer-coated magnet in his left ring finger. The process was a lot cleaner than Anonym’s DIY approach, though Cannon says it would have been far more pleasant with a little anesthetic.

So what’s it like having a sense of magnetism? At first it was a little jarring, Cannon says, to feel his finger buzz like a cellphone on vibrate when it came within a foot of a refrigerator. But over time he has developed an intuitive sense of what’s giving off current, and of what sort (vibrations mean alternating current, a tug means direct). And his little superpower, humble as it is, has come in handy around the house on a few occasions, like when the battery light started flickering on his friend’s laptop. “I went over and hovered my hand over the power brick, hovered my hand over the laptop, repeated that a couple of times, and when I got back to the laptop I felt it kind of sputtering—pop, pop—and I noticed that coincided with the battery light coming on. I said, ‘Hey man, your power bridge is bad.’ ” He says his friend now calls him “the laptop whisperer.”

Cannon and a few like-minded friends formed a collective called Grindhouse Wetwares, with the tagline, “What would you like to be today?” They’ve built such things as a range-finding sensor that makes their fingers pulse based on how far away the nearest walls are. “You can just sweep it over a room and get an idea for the contours of the room with your eyes closed,” Cannon says. “It’s kind of like a sonar sense.” The group has also experimented with implantable biomedical tracking devices and a gizmo called the “thinking cap,” which zaps the brain with electricity in an effort to heighten the user’s focus. (This risky-sounding procedure, known as transcranial direct current stimulation, has actually been shown to boost cognitive performance in several studies, though it may also have its downsides.)

In Barcelona, a nonprofit called the Cyborg Foundation is pushing a more artistic (and less cringe-inducing) vision of sensory extension. It was founded by Neil Harbisson, an artist and musician who was born with achromatopsia, the inability to see colors. Since 2004, Harbisson has worn a device he calls the eyeborg, a head-mounted camera that translates colors into soundwaves and pipes them into his head via bone conduction. Today Harbisson “hears” colors, including some beyond the visible spectrum. “My favorite color is infrared,” he told me, because the sound it produces is less high-pitched. (This prize-winning short film featuring Harbisson is well worth watching.)

The Cyborg Foundation’s co-founder, Moon Ribas, is working on a sensor that can be attached to the back of her head that will vibrate to alert her when someone is approaching from behind. Mariana Viada, the Cyborg Foundation’s communications manager and an outdoorswoman, is looking into an internal compass that could tell her at all times which way is true north. “People ask me why I would want to extend my senses, and I simply answer, ‘Why not?’ ” Viada says. “There is so much out there to discover.”

As low-tech as these types of devices are, Cannon thinks they’re laying the groundwork for more powerful (and pervasive) human enhancements in the future. And he thinks there will be money in it—but he says Grindhouse Wetwares has no interest in becoming a startup beholden to venture capitalists. “We think that in order to preserve ownership of our bodies, we need to make sure this is open-source. If you think Apple has a problem with you jailbreaking your iPhone, wait until they’re responsible for your heart.”

Read more from this series: Human enhancement is giving us superpowers once reserved for comic-book heroes; technology is expanding our minds; and brain-computer interfaces let you move things with a thought.