Smartphones can work as medical labs too

"This method makes heart rate research more inexpensive, portable and straightforward," said James Heathers, the doctoral student from University's School of Psychology behind the project.

"The sensor, placed on a finger instead of using electrodes on the chest, is so small we can mail it to study participants," added Heathers, according to a Sydney statement.

Data on tiny fluctuations in our heart rate provides critical information on the state of our nervous system, and is essential for a range of psychological research including on anger, anxiety, stress and self-control.

At the moment, heart rate variability (HRV) research is done in a university lab with a group of study participants. Electrodes are attached to their chests to measure HRV and the data is recorded, one person at a time, using a lab computer.

"The idea struck me because I'm by nature impatient and my area is psychophysiology which is all about the relationship between physiological and psychological states," said Heather.

"By providing people with a sensor and then using their smartphone to process the data, we are no longer tied down to booking appointments in a university laboratory, and can record dozens of separate data streams at the same time."

Heathers collaborated with Simon Wegerif, a biomedical engineer. Wegerif's company, HRV Fit Ltd, already had an HRV phone app iThlete widely used by professional sports teams and athletes, for whom heart rate variability is an important measurement of their performance and recovery.

The challenge was to adapt a similar app into a tool that can collect and provide HRV data in a way useful to researchers.

"We have run tests of our sensor linked to a smartphone and the software is working very well. I expect it to be up and running and available for free in the next few months," said Heathers.

Heathers plans to use the HRV data to expand theories on the day-to-day fluctuations of the nervous system, and to collect data from groups that are traditionally hard to access.

These results were presented at the Australasian Society for Psychophysiology conference 2012.