Singapore plans to give a wearable device that will identify people who had interacted with carriers of coronavirus to each of its 5.7 million residents, in what could become one of the most comprehensive contact-tracing efforts globally. Testing of the small devices, which can be worn on the end of a lanyard or carried in a handbag, follows limited take-up of an earlier smartphone-based system and has further fuelled privacy concerns about contact tracing technology.