(FORTUNE Magazine) – Imagine the scene: A tight, fist-sized ball of yellow string gets shot 30 feet at a suspect fleeing a crime. As it closes in on him, the ball opens into a 16-foot net that ensnares the bad guy. This is no Spiderman cartoon; police are now using Capture Net--just one of the devices on display at a Denver convention touting technology for cops, paramedics, and firefighters. Like the Capture Net, a lot of the products were backed by the National Institute of Justice, an obscure federal agency charged with boosting research into public safety.

NIJ exists because crime fighting doesn't pay. Local police departments--90% of which have fewer than 30 officers--don't have the budget to develop their own new products. So NIJ pays for research that turns private or military technology into products cops can use. The agency gives out research grants, then serves as a clearinghouse to make sure the findings are available to other companies. (Research that the government funds isn't proprietary.) Recent grant recipients include large public companies like Raytheon, which is developing thermal-imaging equipment able to locate people in the dark, as well as smaller private firms like Integrated Wave Technologies, which has built a mini-translator to spit out phrases like "You have the right to remain silent" in three languages.

Some of the gadgetry rises to James Bond levels. At the Denver convention, NIJ demonstrated a prototype radar flashlight designed to detect subtle movement--even quiet breathing--on the other side of a wall. The agency is also sponsoring research to develop a handheld device that can detect, from seven feet away, whether a suspect is carrying a weapon. It uses audible sound waves that bounce off metal or plastic.

In addition, NIJ has become a kind of Consumer Reports for cops, testing products that are already on the market. One goal is to cut down on sham companies selling bogus devices to the police. For example, it rates bullet-resistant vests and tested an $8,000 device called the Quadro Tracker, which, when powered by the static electricity of a user's breath, purportedly could detect drugs with an oscillator. That sounded too good to be true, and it was. The Quadro Tracker didn't work, leading the agency to issue a warning to police departments across the country.

Also nixed by NIJ--Sticky Foam, the much hyped goo that can be hosed onto fleeing suspects to immobilize them. "It turned out to work a little too well," says David Boyd, director of NIJ's Office of Science and Technology. Boyd's researchers found that it took about ten minutes per square inch to remove the foam from a person's skin, making it too much of a hassle for the police. (The military didn't think so--it has authorized the use of Sticky Foam.)

Some NIJ-funded research goes toward computer applications. The agency gave $3 million to Anser, a not-for-profit research group, to develop software that recognizes people by 35 or so key points on their face. Anser found the facial points work as well as fingerprints in identifying people and originally planned to use it searching the Internet for photos of missing kids. But now Miami drug cops are testing Anser's system to match suspects to a database of mug shots. It's also testing a camera that "learns" the people it watches and alerts a guard if, say, the wrong person takes a bike under its surveillance.

One of the most powerful cop gadgets now in testing is an electromagnetic Auto Arrester that the police can shoot under cars during high-speed chases. Get it close enough, and the Auto Arrestor's magnets shut down the getaway car's engine. That's bad news for would-be escapees, but good news for everyone else on the road. Now if NIJ could only find something to clear up traffic jams.