A red flag for me is the spontaneous development of something that would be completely groundbreaking. I mean all of the people involved are relatively unknown to the scientific community. There should be someone with some kind of credentials who tested and developed the device. A century ago, knowledge and raw materials was usually the limiting factor in discovery and a single genius scientist could make a giant leap in a field because there were a limited number of people total that had access to the knowledge and materials for furthering that area of interest. Today, nearly all of human knowledge lies at the fingertips of anyone with the internet. Everything from genetic sequencing to chemical engineering has become to prevalent and 'cheap' that almost anyone with a good idea have access to all the instruments necesary to achieve 'good science.' Now top this with the multiple Fortune 500 companies that are working to discover a means to non-invasively monitor glucose. Unexpected leaps forward in a scientific discipline, especially in medicine, should be met with great skepticism.
As the saying goes, "extraordinary claims require extraordinary proof."