Icebreaker, a brand of VF Corp., is partnering with a start-up on the development of a smart armband designed to monitor the wearer’s temperature, which could become a key tool in the post-coronavirus world. Nightingale MedTech, the company behind the armband idea, was only formed on May 1. The prototype of the Nightingale Bio-sensor, which has the size of a matchbox, fits into Icebreaker’s merino wool armband. The device automatically assesses body temperature every six minutes.