Since the mid-1990s, companies around the globe have been working on advanced gun safety technology. Indeed, gun safety technology has become a cottage industry of sorts, with small firearms companies eyeing ways to reduce the dangers of firearms.

Of course, as with anything related to guns, there is a debate over whether so-called “smart guns” that rely on technology to increase safety are truly an improvement. Organizations like the Smart Tech Challenges Foundation argue that adding intelligent technology like biometrics can save lives. The San Francisco-based organization, which has granted $1 million to “innovators” working on gun-safety technology, says that with help from the technology industry, it is possible “to make firearms safer for gun owners, their families, and their communities.”

Earlier this year, Democratic senators Ed Markey (D-Mass.) and Elizabeth Warren (D-Mass.) introduced a bill called the “Handgun Trigger Safety Act” and pointed to advances in gun technology as proof that “smart guns” are viable options. The bill, if signed into law, would require handgun vendors to “retrofit” guns with “personalization technology” that would only let the owners shoot them. The bill would also require U.S. handgun makers to produce guns with that personalization technology within five years.

It wasn’t long before critics attacked the bill and the very idea of smart guns. The National Rifle Association’s Institute for Legislative Action says that it’s neither against smart guns nor against Americans owning them. But it “opposes any law prohibiting Americans from acquiring or possessing firearms that don’t possess smart gun technology.”

However, following the mass shootings of the last several years, including the latest attack in San Bernardino, Calif. this week, the call for more gun safety is growing. Meanwhile, technology is advancing in the interest of enhanced gun safety. Here are some of the ideas:

The Aramatix iP1: The Aramatix iP1 resembles a standard handgun, but it comes with a twist: only the owner can fire it. The iP1 will only shoot if it’s within 10 inches of a special watch worn by the owner and must be activated by a five-digit PIN that is valid for just eight hours before it resets. The owner will only be able to fire the gun if the PIN is accurately entered and they’re wearing the watch. If either of those elements is missing, the gun is useless.

The Gun Box: The Gun Box is a safe designed to store handguns in the home. The safe features a biometric fingerprint scanner to ensure only authorized owners can access the firearm inside. In addition, the safe comes with an RFID scanner that can wirelessly open its door when owners are close by. RFID is also built into a ring that owners wear to communicate with, and ultimately open, the box without using a fingerprint.

RFID Guns: Radio frequencies are also being tested for gun safety. The Smart Tech Challenges Foundation is helping to fund firearms that would come with built-in RFID chips capable of capturing and storing information internally. The RFID chips built into the firearms communicate with a ring or watch worn by the gun’s owner. If the RFID receivers are within a few inches of each other, the owner will be able to fire the gun. If not, the gun cannot be fired.

Fingerprint Technology: Several teams at the Smart Tech Challenges Foundation are working on creating biometric technology for guns. The firearms would be built with fingerprint scanners, much like some smartphones. The gun would only shoot after an authorized owner validates his or her fingerprint. The scanners may be placed on several areas on the gun, including the grip.

TriggerSmart: TriggerSmart is another company that has built RFID into guns. Its technology similarly relies on the gun owner wearing a ring that communicates with a small RFID chip in the firearm’s stock or grip. If the firearm is too far away from the ring or someone else tries to use it, the gun will not fire.

Looking ahead, it’s hard to say what the future for smart gun technology looks like. While people are actively seeking ways to make firearms safer, no major gunmaker is selling smart guns on a broad scale. Indeed, in April, Fortune reported wrote about one dealer trying to sell the Aramatix iP1. He asked Fortune not to use his last name or identify where he lives. The reason? He fears for his life. The previous two gun dealers who tried to sell smart guns were threatened by anonymous callers. Those dealers were told they would be put of business, or perhaps, even killed, because they were selling the smart gun.

For more on smart guns, check out the following Fortune video:

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