They're already gathering facial recognition biometrics, and I wouldn't be surprised if they've been doing gait analysis biometric identifiers (it's established tech). Adding heart rate would give them three separate identifiers that can be used to identify anyone in a crowd with practically complete confidence.
[1] https://futurism.com/the-byte/laser-identify-distance-heartb... [2] https://www.ncbi.nlm.nih.gov/pubmed/24111284
They're already gathering facial recognition biometrics, and I wouldn't be surprised if they've been doing gait analysis biometric identifiers (it's established tech). Adding heart rate would give them three separate identifiers that can be used to identify anyone in a crowd with practically complete confidence.