Pulse Response Biometrics

Had never heard of this biometric, but as a student of 'biometrics' was intrigued.   No idea how unique such a signature is.  Article is non technical.

Authentication Using Pulse-Response Biometrics
By Ivan Martinovic, Kasper Rasmussen, Marc Roeschlin, Gene Tsudik 
Communications of the ACM, Vol. 60 No. 2, Pages 108-115 .... 

We propose a new biometric based on the human body's response to an electric square pulse signal, called pulse-response. We explore how this biometric can be used to enhance security in the context of two example applications: (1) an additional authentication mechanism in PIN entry systems, and (2) a means of continuous authentication on a secure terminal. The pulse-response biometric is effective because each human body exhibits a unique response to a signal pulse applied at the palm of one hand, and measured at the palm of the other. .... "