Everyone, including ship's records officers, has a heartbeat with a unique auditory signature. A new device developed for U.S. Special Forces can be used to tell them apart [technologyreview.com] similar to irises or fingerprints even at a distance.
[The] new device [...] can identify people without seeing their face: instead it detects their unique cardiac signature with an infrared laser. While it works at 200 meters (219 yards), longer distances could be possible with a better laser. “I don’t want to say you could do it from space,” says Steward Remaly, of the Pentagon’s Combatting [sic] Terrorism Technical Support Office, “but longer ranges should be possible.”
The device, dubbed 'Jetson' uses laser vibrometry to detect surface vibrations the heartbeat causes on skin, clothing, or jackets (though it is not effective through very heavy clothing such as thick winter coats)
Cardiac signatures are already used for security identification. The Canadian company Nymi has developed a wrist-worn pulse sensor as an alternative to fingerprint identification. The technology has been trialed by the Halifax building society in the UK.
The developers of the technology indicate that this could likely also be adjusted to scan for heart issues such as arrythmias remotely.