The robots, produced by the California tech startup Knightscope, are intended to assist in crime prevention and law enforcement.
They are equipped with a 360-degree camera, thermal imaging, automatic license plate recognition, directional microphones, proximity sensors and other technologies.
Their "anomaly detection software" is designed to determine if there is a threat, and alert appropriate authorities.
Knightscope was founded in response to the 2012 mass shooting at Sandy Hook Elementary School in Connecticut and the 2013 deadly bomb attack near the finish line of the Boston race, according to the company's website.
The company claims its robots are not intended to replace humans but to help security and law enforcement be more effective.
Others in the sector include Colorado-based Gamma 2 Robotics, which aims at warehouses, data centers, manufacturing facilities and retail stores, and California-based SMP Robotics, which makes outdoor robots and is marketing in Brazil, France, Japan, Singapore and the United Arab Emirates.