In the days before coronavirus, you may have thought Bluetooth was mostly used for hooking up a wireless loudspeaker to a favourite music playlist on your phone as you relax in a park on a sunny afternoon.
But now the short-range radio technology - named after a 10th-century Danish king - may hold the key to halting the spread of the virus, a group of European scientists has announced.
A new smartphone app could help health authorities to trace people who had come into contact with those infected with coronavirus.
It works by keeping a record of when a phone comes within close range of another, so that should an individual test positive for the virus, others at risk of infection can be quickly identified.
The ability to track down those at risk of infection more accurately could make it possible to ease country-wide lockdowns that have brought economic activity in many countries to a near halt.
The initiative, named Pan-European Privacy Preserving Proximity Tracing (PEPP-PT), follows the successful use of smartphones in some Asian countries to track the spread of the virus and enforce quarantine orders - although the methods used in several of those countries would likely violate strict European Union data protection rules.
PEPP-PT, which brings together 130 researchers from eight countries, aims to launch its platform by April 7, said Hans-Christian Boos, founder of German tech startup Arago and a member of Chancellor Angela Merkel's digital advisory council.
Merkel, in isolation after being treated by a doctor who tested positive for COVID-19, said she would recommend such an app as long as it was effective and voluntary.
"I would, of course, also be prepared to use it myself to help other people," the conservative leader told reporters.
Epidemiologists say contact tracing will become a vital weapon in containing future flare-ups in COVID-19, the flu-like disease caused by coronavirus, once national lockdowns succeed in slowing the rapid spread of the virus.
"We all know that, as a society and an economy, we cannot go on like this for an extended period of time," Marcel Salathe, professor of digital epidemiology at the Swiss Federal Institute of Technology in Lausanne, told a news briefing.
"There is a more efficient way to break this exponential trend of growth."
The illness can be passed on by people showing no symptoms, putting a premium on warning those at risk of infection swiftly after an individual tests positive.
The new platform would make anonymous use of low-energy Bluetooth technology in a way that respects the EU's General Data Protection Regulation (GDPR), and would not require the intrusive tracking of location data.
It would log connections made between smartphones on a device, rather than a central server, for two weeks, using strong encryption. Only local health authorities, deemed "trusted persons", could download data so they could notify people at risk of infection and tell them to go into isolation.
A study by researchers at Oxford University's Big Data Institute said 60 percent of a country's population would need to be involved for the approach to be effective. Those without smartphones could wear Bluetooth-enabled armbands.
German research body Fraunhofer Heinrich Hertz Institute (HHI) has worked on the technology platform with Vodafone and others. It has recruited volunteers from the German army to measure how different smartphone brands communicate with each other.
The PEPP-PT project is similar to Singapore's TraceTogether app, but differs in some respects - for one, by using country codes, it can work across borders, said Fraunhofer HHI head Thomas Wiegand.
Separately, a group of Berlin startups, led by data management company via, fintech group finleap and insurance tech firm Wefox Group, said it planned to launch its own contact-tracing app named Healthy Together next week.
Sascha Gartenbach, founder and chief executive of via, said the Healthy Together group was in touch with PEPP-PT on collaborating. "Our approaches are complementary," he told Reuters.