Some governments want a technological silver bullet to solve the public health crisis. But many of the tools aimed at solving problems come with a host of other problems that will undermine the public health goals for which they are adopted, and create new unintended consequences for privacy, association, and freedom of expression.
These electronic devices are usually worn on the wrist or ankle. Their use can be mandated by the government or voluntary (although users don't always understand exactly what it is they're being asked to wear). We might tend to associate the idea of a "wearable" with either a smartwatch or an ankle monitor, but governments are also using wrist-worn "bracelets" for a broad range of different purposes amid the COVID-19 pandemic.
Wearables may use an electronic sensor to collect health information from the wearer (by measuring vital signs) and act as an early warning to identify likely COVID-19 patients before they show any symptoms. They can also be used to detect or log people's proximity to one another (to enforce social distancing) or between a person's bracelet and that person's own mobile phone or a stationary home beacon (to enforce home quarantine).