Now Playing: 04-04-12 Marketplace Tech Report

A new report from the American Civil Liberties Union says that law enforcement agencies are frequently using cell phone tracking information provided by wireless carriers. The ACLU claims the information is readily available, and that police are interested in figuring out where people go and what they do. But what is that info being used for? Finally, scientists at MIT have developed these tiny magnetic blocks that can communicate with one another and come together to replicate objects.