A prototype smart ring developed by engineers at the University of California appears to have cracked one of the holy grails of health wearables: non-invasive blood sugar measurement. The data is sent to a companion app on a paired iPhone.While existing smart rings rely purely on biophysical data extracted from sensors like those embedded into the [Apple Watch](https://9to5mac.com/guides/apple-watch/), this ring also tracks chemical biomarkers by analysing sweat …