Daniel Wilson, a Ph.D. in robotics who works on practical applications for computer vision and artificial intelligence, said Riya is "a great idea."

"Face recognition is really hard," he said. "With Riya, they've constrained the problem."

Wilson explained the system works because it is cleverly constrained: It looks for a limited set of attributes in a limited set of photos.

For his part, Wilson, author of How to Survive A Robot Uprising, said people concerned about being identified against their will shouldn't worry too much.

"If the system could be used that broadly," said Wilson, Riya wouldn't be talking about consumer applications. "They'd be talking to the Department of Homeland Security."