However, at times of rapid change, mainly due to blood flow variability, levels from alternate sites differ considerably.
Diffusion of glucose from plasma to IF is in proportion to the concentration in each compartment.
I'm quoting different sections of the NCBI article, but the overall point is that there's a good correlation in glucose from blood to IF, but the rate of diffusion means that IF measurements won't register changes as quickly, so if blood glucose spikes suddenly or drops very quickly, it will just read as a gradual increase or gradual decline, so I think it would be dangerous for a diabetic to use it for determining insulin dose or anyone monitoring for hypoglycemia, etc.
That flattening of the response in the IF measurement wouldn't deter me from using it to monitor my glucose levels over time, but if I were still an active T2DM, I would test postprandially at T60 and T120 if there were problems.
If the price were right, I would definitely want one!