We - at DiaMonTech - are working on non-invasive glucose monitoring for over a decade now. It's a hard and complex problem and as long as clinical data is missing, I'm very sceptical.
We just reached (in a clinical trial) a comparable accuracy as early-stage invasive devices that got FDA approved with a shoe-box-sized device and we still have some work to do. The pre-print of our publication is here: https://www.researchsquare.com/article/rs-5289491/v1
I'm excited to see new developments but in this case, I'm not sure this will reach the market anytime soon.
Last Chance to See by Douglas Adams - it's a book from the early 90s and Douglas Adams travels the world to see the world’s most endangered and exotic creatures. It's heart breaking and at the same time written with such a delight that it is fun to read. I cannot explain it better but highly recommended.
(unfortunately it's in German - but there is an english live translation available)