Amazon Key is expanding into vehicles as it is now able to deliver packages straight to the trunk of unattended cars parked in a public space.

Last year, Amazon first launched Amazon Key as a new means to deliver packages more easily. With Amazon Key, the company's delivery drivers could unlock users' door and leave the package inside, even if no one is home.

The program sparked some controversy and safety concerns, but it ultimately saw positive reception and it's now expanding to cars as well. It's currently available for Amazon Prime members with eligible vehicles.

"As a Prime member, get your Amazon packages securely delivered right into your vehicle parked at home, at work or near other locations in your address book," says Amazon. "Park your vehicle in a publicly accessible area to receive in-car deliveries, and track your packages with real-time notifications."

Amazon Key for in-car deliveries is free for Prime members in select cities and areas, provided that their vehicles are compatible.

Amazon Key In-Car Delivery: Security Measures

For those who are worried about security and think that it couldn't possibly be safe to have a stranger unlock their car to leave a package inside the trunk, Amazon highlights that it has taken several security measures.

First of all, it's not Amazon that unlocks the vehicle, but the car's manufacturer. In an exclusive demo for The Verge, Amazon mentioned four such security measures designed to ease users' concerns and ensure that it all goes without incident.

"Note that [the Amazon delivery driver] doesn't have a special key or direct access to the car," The Verge explains. "It's going up to the Amazon Key cloud, and it's going over to the Chevrolet cloud, in this case, which is where the unlock command is issued. We only actually do the unlock if its [sic] the right person, right place, right car, right time. Got to pass all those checks."

Amazon Key In-Car Delivery Perks And Limitations

In-car delivery could prove to be useful in a number of scenarios when one might want their package delivered someplace other than their home or workplace. Those throwing a surprise party, for instance, would prefer to have party supplies delivered to the trunk of their car so as not to tip off the person getting the party.

One can get the package without having to be present or signing for anything, they'd simply find it in the trunk of their car. They would get notifications once it's there, and they would have to make no additional effort.

At the same time, there are also a number of limitations, at least for now. For the time being, Amazon Key in-car deliveries will become available in 37 cities across the United States, but only for a limited number of vehicles and models.

Most Chevrolet, Cadillac, Buick, and Volvo vehicles from 2015 or newer, with a connected car service enabled, will be able to support the new in-car delivery system from Amazon Key. Amazon plans to add more supported vehicles and models in time, but for now, that's it.

To get a better idea of how things work, check out the video below.