It uses two electromagnetic sensors- a multiband slot antenna (worn in a glove on the hand) and a multiband-reject filter (worn on the forearm). They can work independently but using them together helps tailor it for differences in individuals.
Scroll down to figure 5 to see the results of human testing during a glucose tolerance test to see the reference (red) as compared to the CGM data (blue dots and line). Looks impressive. It might be annoying to wear a glove all the time, but zero lag time might be worth it to some people.