Heartbeats could be measured wirelessly

Spread-spectrum is a form of wireless communication that varies the frequency of transmitted signals in order to obtain a greater bandwidth.

Traditional methods for measuring heart rate - stethoscopes, fitness trackers and armbands are all regularly used to track heart rate. Researchers hope the new technology will allow "casual sensing" - measuring people's heart rates as they go about their day to day life.

"Taking measurements with sensors on the body can be stressful and troublesome," said Hiroyuki Sakai, lead researcher on the project. "We tried to make something that would offer people a way to monitor their body in a casual and relaxed environment".

It's not the only hands-off way of measuring vital signs - two technologies have emerged from MIT labs recently that have similar functions. One, an ingestible sensor, uses microphones to send sound waves to an external sensor. Another, a smartphone, uses a phone's inbuilt accelerometer to "capture the small movements of your body that result from the beating of your heart".