[plato]

At any reasonable distance, the "operators "signature would be equal to that of the person sought so you would need to know the location of the "subject" in advance. The electrical eminations from a human body are not directional. Therefore, the human heartbeat of one person sought, would be "detectable" in front of you, behind you, and in all directions.

It's sorta like standing in the middle of a football field, blind, and picking up the heartbeat of someone with a red shirt, as opposed to every one else.

Basically, nope, no way, not a chance.

Over 30 years as a pretty da**ed good engineer.