Taking the iWatch "send your heartbeat" feature to the next level! Nymi leverages a person’s heartbeat as a biometric identifier. Nymi has partnered with MasterCard and the TD Bank Group to authenticate payments. http://www.psfk.com/2015/08/pay-...

Cool idea. How do you normalize for changes in beat-to-beat heart rate variability? Say, if I'm stressed? Or went for a run recently? Or to take an extreme case, if I have an arrhythmia?