“If we can set it up so you can’t unlock your phone unless you’ve got the right fingerprint, why can’t we do the same thing for our guns?” Obama said. "If a child can’t open a bottle of aspirin, we should make sure that they can’t pull a trigger on a gun. Right?”

The technology Obama described seems possible, certainly, but it isn’t necessarily straightforward. That’s for a few reasons. For one thing, gun owners often want their weapons to be instantly accessible and usable. That’s why so many people choose not to store their firearms in safes. According to one American Journal of Public Health study, there is at least one unlocked firearm in 43 percent of homes with guns and children in them in the United States; and 9 percent of homes have guns that were kept unlocked and loaded.

The system Dual:Lock built attempts to solve this safety problem with an external safe that essentially keeps the gun locked in its holster until the authenticated user reaches for it. “The thumb aligns perfectly on the sensor, so that movement of grabbing the gun unlocks it,” Oh told me.

Making guns personalized so that they only work for approved users is a major theme in gun-safety technology today, but not everyone agrees that fingerprint sensors are the way to go. “A biometric solution is a great solution for someone who is not in inclement weather, or someone whose hands aren’t going to be dirty,” said Margot Hirsch, the president of the Smart Tech Challenges Foundation, which offers grants to individuals working on gun safety. “So then you’ve got RFID, which uses radio frequencies, and only allows the firearm to discharge when the gun owner places a corresponding token—like a ring or a bracelet—in very close proximity to the trigger.”

Authentication that uses RFID, short for radio-frequency identification, might be better for law enforcement or a hunter, for example. “Or someone perhaps a little more recreational,” Hirsch said, “Because you can still wear a glove. Your hands can get dirty or wet.”

Among those advocating for improvements to gun-safety technology, the biggest challenge may be getting people to buy the guns equipped with them. One buzzed-about smart-gun company, Armatix, has had a difficult time gaining traction. Its handgun, which used an RFID authenticator linked to a wristwatch, was the first firearm of its kind to reach the market. Armatix went through a bankruptcy-like restructuring last spring, after many people criticized the relatively high price of its guns. A review by America’s 1st Freedom, a publication run by the NRA, called Armatix’s smart weapon “sleek” but unreliable and ultimately “disappointing.” The review also raised questions about remote hacking, an aspect of personalized authentication that is likely to continue to come up.

“Some guys sniggered that [Armatix’s] .22 was for shooting squirrels,” said Robert McNamara, the founder of TriggerSmart, another company building a weapon authenticator. “The purists of the gun world would’ve considered it a peashooter. As is often the case, the pioneers make mistakes and the next wave of people who come along benefit from that.”