Researchers at the Georgia Tech Research Institute have developed a radar that will detect heartbeat and respiration without any physical connection to the subject. The system is capable of making these measurements at ranges exceeding 10 meters. This paper explores the use of the system for the biometric identification of personnel who work in a highly secure environment. The system, used in this application, would use the heartbeat signature of an individual as a biometric identifier. Also, the system could be used to determine the stress level being experienced by an individual on the basis of respiration and heartbeat rates.
Eugene F. Greneker,
"Radar sensing of heartbeat and respiration at a distance with security applications", Proc. SPIE 3066, Radar Sensor Technology II, (10 June 1997); doi: 10.1117/12.276106; https://doi.org/10.1117/12.276106