Don't know names off the top of my head, but sure I read that there was development of glucose monitoring from changes in eye's which would be non invasive.
A quick Google of "non-invasive glucose monitoring" comes up with quite a few solutions and approaches. What is your reason for asking @Rabdos ? Are you interested in a specific approach that you have read about?
I have been trying to figure out what is the state of the art in this sector. That Glucowise thingy is "in development" for the last 5 years at least, since I came across it, it is like a scam. Are there any big companies interested in minimally invasive glucose monitoring without penetrating the skin? I have not been able to identify any big one working or interested in the subject.