In the recent edition of New Scientist, Victor Lubecke and Olga Boric-Lubecke, who are heading the project, explained that they had noticed that some of the microwaves transmitted by a cellphone’s antenna bounced back to the phone from the chest, heart, and lungs of the person using it. The project is based on the fact that when organs move, the frequency of the reflected radiation shifts slightly, referred to as the Doppler shift. For example, when the lung expands, the radiation bouncing off it is pushed closer together, slightly raising the frequency, and lowers it when it contracts.

The engineers at the Bell Labs intend to modify the mobile phone with a circuit that detects the Doppler shift in the reflected signal packed by its antenna. The information is then sent on to the base station where further signal processing extracts the user’s vital signs, the magazine said.

As long as the cellphone is on and held steady for a few seconds, the reflected signals can be picked up. This is what happens if the user is trapped or unconscious, said Lubecke. In addition, physicians could use the technology to monitor a patient’s heart rate or breathing, by simply calling the patient’s cellphone.

For the new system to work, networks would have to be modified to prevent the interference information from being discarded as noise. According to the researchers, a simple software change would be necessary for the network to retain and interpret the signals.

Other experts told the magazine that they are doubtful that the Bell Lab technology will work, as the weaker heartbeat signal would be swamped by the stronger main signal.