An Amazon patent application sheds light on a way to monitor neighborhoods with a doorbell camera that could alert homeowners and police of suspicious activities and people. The patent application, which was made public on the United States Patent and Trademark Office website Thursday, describes how a network of cameras could work together with facial recognition technology to identify people, and respond accordingly. Amazon’s application says the process leads to safer, more connected neighborhoods, as well as better informed homeowners and law enforcement. The application describes creating a database of suspicious persons. Unwanted visitors would be added to the list when a homeowner tags them as not authorized. Other people could be added to the database because they are a convicted felon or registered sex offender, according to the application. Residents may also alert neighbors of a suspicious person’s presence. But some people, such as a mail courier, could be placed on an authorized persons list. Postal service logos could be used to help identify them. The patent describes the neighborhood surveillance system as an opt-in service. Some critics expressed concern to CNN Business about the implications of the broad use of facial recognition technology. “The patent is a roadmap for Amazon’s disturbing vision of surveillance in the future,” Jacob Snow, a technology and civil liberties attorney with the American Civil Liberties Union, told CNN Business. “People have the right to go about their daily lives without being watched and tracked. And there’s no assurance the resolution of the doorbell camera is very good.” This summer, the ACLU tested the software and showed that it inaccurately identified some members of Congress as criminals. The patent’s inventor is listed as Jamie Siminoff, CEO of Ring, which Amazon acquired earlier this year. Companies often patent ideas that never come to fruition. But Amazon has shown a willingness to use facial recognition technology elsewhere. In May, Amazon’s Ring announced a social network called Neighbors, which was created for sharing photos and videos of burglars, suspicious activity and package thieves. The technology described in the patent could make the platform more powerful. “We are always innovating on behalf of neighbors to make our neighborhoods better places to live, and this patent is one of many ideas to enhance the services we offer. Patents do not necessarily reflect current developments to products and services, and this patent certainly does not imply implementation,” a Ring spokesperson said in a statement. “Privacy is of the utmost importance to us, and we always design our services to include strong privacy protections.” Amazon’s competitors in the home security space have already embraced facial recognition technology. Some of Google’s cameras, including the Nest Hello and Nest Cam IQ, already identify faces and identify users. Meanwhile, French startup Netatmo sells an indoor camera that uses facial recognition technology. Amazon seems aware of some of the technology’s current limitations. The patent application details how it may be difficult to get a clear photo of a person’s face, but it also describes the value of sharing data with other neighbors. If multiple cameras capture the same person, the images could be stitched together to create a composite image. The composite image may be sent to the homeowner’s smartphone, according to the application. According to Matt Pruitt, chief solutions architect at NEC, which develops facial recognition technology, Amazon’s algorithms would benefit from a mass deployment of the technology. Amazon cameras would regularly capture people entering their homes, allowing it to test and improve on how well it identifies people. He expected the potential surveillance of neighborhoods to be limited to front porches, as the doorbell cameras lack the power to identify people farther away on sidewalks or streets. “Smart city or surveillance state are two sides of the same coin,” Pruitt said. “Technology in itself is neither good or bad. It’s how it’s used in the end.” Update: This story has been updated with a comment from Amazon.