That's how the Glucotrack claims to work. From their site: GlucoTrack uses ultrasonic, electromagnetic and thermal technologies to non-invasively measure gluco

That's how the Glucotrack claims to work. From their site: GlucoTrack uses ultrasonic, electromagnetic and thermal technologies to non-invasively measure glucose levels in the blood. GlucoTrack is intended for use by Type 2 and pre-diabetics. GlucoTrack combines the following technologies: Ultrasound (speed of sound change within the tissue); Electromagnetic (conductivity of the tissue); Thermal (heat capacity of the tissue). It's not approved by the FDA, but it appears to be selling in Australia, New Zealand, Spain, China, Korea, Italy and some others.