Bulgaria is the latest country to test a wristband that can track people during the coronavirus pandemic.
Up to 50 residents in Sofia will be given a device that can record their movements using GPS satellite location data.
Several nations are testing similar wristbands to make sure people are obeying orders to stay at home.
South Korea and Hong Kong have also been using electronic trackers to help enforce quarantine.
The trial in Bulgaria will use Comarch LifeWristbands, developed in Poland.
As well as confirming a person is staying at home, the device can monitor the wearer’s heart rate and be used to call the emergency services.
In South Korea, people found to be violating quarantine rules can be ordered to wear a tracking band.
The device was introduced after people were caught leaving their smartphones at home to avoid detection.
The band can alert the authorities if the wearer leaves home or tries to remove the device.
Campaign groups, including Privacy International, have warned that the coronavirus pandemic could be used as a “power grab” by some governments.
It has said new measures should be “temporary, necessary, and proportionate”.
“When the pandemic is over, such extraordinary measures must be put to an end and held to account,” Privacy International said in a blog post.
Other places testing wearable gadgets include:
- Belgium, where residents are testing a social distancing wristband that vibrates if it comes within 3m (9.8ft) of another band
- Lichtenstein, where one in 10 residents will be given a band to track “temperature, breathing and heart rate, and transmit it to a lab in Switzerland for further investigation”. Later this year, a further 38,000 residents will be given a band
- India, which has announced plans to manufacture thousands of location and temperature-monitoring bands for people in quarantine
- Hong Kong, where police can be alerted if people wearing an electronic band leave the house while under quarantine
Wearable devices could also help the adoption of contact tracing.
Contact tracing aims to keep a record of who a person has been close to for long enough to catch coronavirus, so cascades of alerts can be sent if they test positive for Covid-19.
Apple and Google have proposed a privacy-focused method using Bluetooth to automate the process, which the UK’s NHSX is also exploring.
However, about 12% of smartphones in the UK lack the Bluetooth Low Energy (BTLE) functionality needed for it to work.
Some researchers suggest simple Bluetooth wristbands could be used by people who do not own a smartphone.
“It would be an option to increase coverage and there are also cheaper Bluetooth devices that could have the basic functionality without being a full smartphone,” said Christophe Fraser from the Oxford Big Data Institute.
“Wearable Bluetooth devices could indicate in a very basic way whether contact has been made.”