The service uses a smart lock and connected camera, along with an app, to provide home access to guests. Of course, the highly touted feature is being able to take deliveries when no one is home. When a delivery person has a package, they can scan the barcode, which will unlock the door. The entire thing happens through an app, and it's recorded, so you know exactly what is happening while the courier is in your home. After they leave, they simply lock the door, and that's it.

Customers can choose from eight different smart locks (including five more options added today) that are available from leading manufacturers, like Kwikset and Yale. And right now, Amazon is running a promotion where users can receive anywhere from $110 to $140 off of a Amazon Key Home Kit, depending on which one you choose.

Since Amazon is now offering some Amazon Key features across the US, it's probably only a matter of time before the company expands in-home deliveries to more cities as well. There are certainly some privacy concerns with the service, but the company introduced fingerprint authentication back in March, so that should certainly help with some of the hesitation.