Soon the U.S. military will have something akin to X-ray vision. Researchers at the Defense Advanced Research Projects Agency are working on improving its sensors to track a person's heartbeat through walls and even pinpoint it in a crowd.

Called "Biometrics-at-a-distance," DARPA's program seeks to build sensors that can record human vital signs greater than 10 meters using non-line-of-sight methods and do so for up to 10 people at the same time.

The program will essentially be a blend of two existing Pentagon projects: the Radar Scope and the LifeReader. The Radar Scope was developed in 2006 and uses radar waves to see through walls and detect the subject's breathing. The Life Reader is a system that uses Doppler radar to find heartbeats. The military has also been using scanners like "Sense Through the Wall" and TiaLinx's Eagle scanner that can detect the presence of humans and animals through walls.

DARPA seeks a system that can combine all these technologies into one device that can do it better. It's planned "Biometrics-at-a-distance" will be able to see much farther than current sensors. Some see-through devices can only see through eight inches of concrete, but DARPA is working on a device to see farther than 10 meters in crowded areas. Seeing or "sensing" if there are enemies through walls will be a big help to troops and even police officers who will be one step ahead of what's on the other side of the door.

DARPA is also adding another feature that will make it harder for fugitives to hide from their sensors. A person's heartbeat is unique to the individual so DARPA is going to use electrocardiography, the analysis of the heart's electrical activity to identify up to 10 different individuals.

The new sensor won't just be used for military applications. Having the ability to find heartbeats will be helpful in disaster rescue efforts where victims could be trapped under miles of rubble.