Their head-mounted flashlights swaying in the darkness, workers at the Bodega Andres Morate vineyards resemble fireflies from a distance as they roll their wheelcarts from one vine to another cutting grape bunches at night.

South Koreans may soon be able to carry a device inside their own bodies in the form of a bespoke tattoo that automatically alerts them to potential health problems, if a science team's project bears fruit.