Building technology is all about learning as you go. Amazon knows this, and has today added fingerprint ID to the new Amazon Key app, which enables in-home delivery of goods.

The Key app was announced in October, alongside the Cloud Cam, which lets users watch goings on in their homes as delivery professionals come in and out of their space.

Given that the app essentially controls who gets in and out of your home, it would be problematic if your phone got into the hands of someone malicious. So Amazon has added an additional layer of security, your fingerprint, to the Android version of the app.

An Amazon spokesperson told TechCrunch that fingerprint authentication is coming soon to iOS.

Amazon recently acquired smart doorbell maker Ring in a deal reportedly valued at $1.1 billion, which presumably furthers the mission of truly last mile deliveries. Late last year, Amazon also acquired security startup Blink for a reported $90 million.

But Amazon isn’t the only one dabbling in in-home deliveries. WalMart partnered with August Lock last year to allow delivery people to bring groceries and other goods all the way into the home and put them away.

Amazon CloudCam is available starting at $199, but the door lock used with the Key app is sold separately.