A Philadelphia start-up called ROAR for Good is marketing jewelry designed to emit a loud alarm when its wearer is being assaulted. In the Netherlands, Pearltect is offering a bracelet it says will give off a strong, disgusting odor — “a clear signal that its wearer says NO!” And in 2014 a group of (male) engineering students at North Carolina State won an entrepreneurship award, plus $100,000 in venture capital, for inventing a nail polish said to change color when exposed to date-rape drugs.

Not since the chastity belt, it seems, has there been so much interest in technology to prevent sexual violence.

But are devices like these — and even more lurid ideas, like the Rape-aXe, a female condom studded with spikes — really effective? And what do they tell us about society’s response to the pervasive problem of sexual violence?

Sexual assault has historically been viewed as the result of men’s inability to control their sexual desires. To avoid being raped, this line of thinking goes, women should avoid enticing men. Women have been encouraged to stay home, for example — especially at night. They are instructed to dress modestly, and to avoid compromising positions with men who might succumb to their uncontrollable urges.

The chastity belt was an extreme embodiment of this view of sexual dynamics. “The whole contraption is a symbol of male control and is a monstrous idea for protecting women,” says Albert Classen, professor of German studies at the University of Arizona and author of “The Medieval Chastity Belt: A Myth-Making Process.” And while the belt existed only in satire by the 19th century, there is some evidence that women entering the factory workforce during the Industrial Revolution would, indeed, wear “rape shields” — essentially, reinforced underwear — to protect them from their male bosses.

By the 1960s, second-wave feminism brought about a new concept of rape, one that viewed it as a tool to keep women subordinate to men. “The threat of rape is used to deny women employment,” wrote feminist and poet Susan Griffin in her 1971 essay “Rape: The All-American Crime.” “The fear of rape keeps women off the streets at night. Keeps women at home. Keeps women passive.”

This shift in attitude led to new tactics to prevent sexual assault: Rape “shield laws” barring a woman’s prior sexual history from being used against her; laws against marital rape; and the criminalization of statutory rape. More recently, third-wave feminism has gone further, promoting campaigns like Take Back the Night and SlutWalk, and demanding changes in how sexual assaults are handled on university campuses.

Unlike old prevention techniques, the new technological approaches acknowledge that a woman has the right to be in public spaces, to spend time in the company of men, and even to drink alcohol. For the makers of these products, their motivations are simple. “I want to protect women against possible rape,” says Rape-aXe’s creator, Sonnet Ehlers, in an interview with Mother Jones magazine. (She declined to comment for this article.)

And they have been rewarded for their desire to change the world. Last year, Pearltect’s malodorous bracelet received 50,000 euros (about $56,000) from the Dutch technology giant Philips as the winner of their prestigious Philips Innovation Award. Guardian, a jewelry alarm, took home a DST-Lockheed Martin Innovation Award In India. Undercover Colors, the nail polish meant to detect the date-rape drug GHB, won its inventors $11,250 from North Carolina State’s Entrepreneurship Initiative and subsequently received $100,000 in support from an investor who saw their demo.

Yet despite the 21st-century feel of a necklace that can send your GPS coordinates to the police, most of these technologies are not truly new. The analog versions have existed for years, we just call them by more common names, like knives, guns, and pepper spray. Modern rape-alert technology, meanwhile, is as old as humanity itself, and we know it better as screaming. And in any case, the effectiveness of all this newfangled anti-rape tech is woefully understudied.

“They are stupid and ineffective,” says Kristen Houser, chief public affairs officer of the nonprofit Pennsylvania Coalition Against Rape. “If these things worked, we would have solved rape by now because we’ve been doing it since the beginning of time.”

Nor is it clear that their high-tech successors will work as advertised. There are serious questions about whether the Undercover Colors nail polish can detect GHB, and the inventors have yet to produce a working prototype. (They also declined requests for an interview.) Rape-aXe and Pearltect have only created prototypes, and the products are not commercially available.

But even if they work as intended, what these devices fail to acknowledge is that most rapes are committed by someone known to the victim. It is all very well to insert your spiked condom ahead of a potential walk through deserted streets, but according to the Centers for Disease Control and Prevention, 92 percent of all rapes are committed by someone known to the victim. A battered spouse is unlikely to fill her own home with noxious gas to deter her abuser, or sound an alarm to alert a friend.

“These kinds of technologies show a shocking lack of understanding of sexual violence,” says Nynke Tromp, assistant professor of social design and behavior change at the Delft University of Technology in the Netherlands.

Even in “stranger rapes,” the devices are problematic. Rape-aXe, for instance, would not actually prevent a rape; it is designed to work only after a victim has been penetrated.

In any event, “the moment of rape is not the best instance to intervene,” says Tromp. Better, experts say, to spend more time and resources understanding they psychology of sexual predation itself. Studies of rapists, for example, suggest that they often distort their thinking in order to justify their behavior. Many hold views that are sexist and misogynist. And convoluted discussions of sex and consent can make it easier for predators to rationalize rape.

“We want to see prevention efforts focusing on all of the things before you get to criminal behavior,” says Houser.

Short of that, these technologies strike some experts as walking a fine line between protection and victim blaming. After all, despite shifting views of sexual assault, it’s remains common for victims to be questioned about their own behavior prior to a rape — as in, “What was she wearing?” In Texas in 2011, after an eleven-year-old girl was gang-raped by as many as twenty men, The New York Times quoted neighbors as saying “she dressed older than her age, wearing makeup and fashions more appropriate to a woman in her twenties.” A man in Australia was acquitted of rape after a judge asserted that the victim must have collaborated in the removal of her skinny jeans.

If eleven-year-olds are blamed for how they dress, it is not a stretch to begin blaming women for failing to wear a bracelet or necklace designed to prevent sexual attack.

“You’ve increased the responsibility on the person who is vulnerable,” says Tromp.

There’s also the risk of escalating violence. What happens to a victim, for example, when the rapist is sprayed or shocked, or when he finds himself with spikes attached to his penis? Sexual assault, like other forms of human interaction, is exceptionally complicated, critics of these technologies suggest, and simple solutions to complicated problems are rare — even with innovation prizes and investors backing them.

Of far less interest to venture capitalists are three programs — Safe Dates, Real Consent and Shifting Boundaries — that have been shown to be effective in preventing sexual assault, according to the CDC. All three are extensive educational efforts aimed at young people of high school or college age, and they focus primarily on the importance of consent, bystander intervention, and healthy relationships. This doesn’t mean technology has no role to play, but it does suggest that more needs to be done to shift the focus from the immediate problem of sexual violence, and toward its underlying causes. In part, that would involve moving industrial design “away from a classical problem-solving approach,” Tromp noted, “and examining problems from a systems perspective.”

Houser has one idea: “Perhaps video games,” she suggests, “that encourage people to communicate rather than killing.”

Molly Quell is an American writer and social media consultant based in the Netherlands. She is currently the international editor for Delta, the campus magazine for TU Delft.