Texting, browsing, playing games, taking directions, listening to music are the things you use your cellphone for. But now it can be used to fight diseases.
Cellphones would start a fight against diseases by relaying a telltale signature of illness to doctors and agencies monitoring new outbreaks.
"This technology is an early warning system," New Scientist quoted Anmol Madan of the Massachusetts Institute of Technology as saying.
Madan's team concluded that you could spot cases of flu by looking for changes in the movement and communication patterns of infected people.
This technology could be an early warning system to enable us to pot outbreaks of influenza
Epidemiologists know that disease outbreaks change mobility patterns, but until now have been unable to track these patterns in any detail.
So Madan and colleagues gave cellphones to 70 students in an undergraduate dormitory. The phones came with software that supplied the team with anonymous data on the students' movements, phone calls and text messages.
The students also completed daily surveys on their mental and physical health.
A characteristic signature of illness emerged from the data, which was gathered over a 10-week period in early 2009.
Students who came down with a fever or full-blown flu tended to move around less and make fewer calls late at night and early in the morning.
When Madan trained software to hunt for this signature in the cellphone data, a daily check correctly identified flu victims 90 per cent of the time.
The technique could be used to monitor the health status of individuals who live alone.
Madan is developing a smartphone app that will alert a named contact, perhaps a relative or doctor, when a person's communication and movement patterns suggest that they are ill.
Public health officials could also use the technique to spot emerging outbreaks of illness ahead of conventional detection systems, which today rely on reports from doctors and virus-testing labs.
The findings were presented at the International Conference on Ubiquitous Computing in Copenhagen, last month.