Today’s invention is used to prove one’s status as a person, and not a robot, when eg signing up to something online.
One attaches a microphone/stethoscope to one’s wrist and connects this to the computer being used. This records a snatch of heartbeat data.
Then the computer selects some task at random which is designed to change the heartbeat response in some broadly predictable way (such as presenting a small stress-inducing spelling test or coordination task).
This makes it much more difficult for automated systems simply to play a recording of some person’s heartbeat patterns.
A system might be devised which could identify individuals from their cardiac behaviour under different forms of stress.