We've had ways to measure glicose non-invasively since the 90s, but since we're dealing with human lives - glucose monitoring is a matter of life and death for people with diabetes - such a device must be at least as accurate as finger-stick meters. None has come close so far.
This thing doesn't need to be anywhere near that accurate to be useful to someone. Fitness monitors are already pretty inaccurate but they're useful to get a general idea of your activity levels from day to day.
Trying to guess how many calories are in your food and adding them up each day isn't accurate, so a device that tries to measure it automatically based on your physiology only has to be that accurate. Maybe within 30% would still be useful to people tracking their fitness.
Obviously someone who is tracking their glucose or caloric intake for medical reasons should use FDA-approved medical devices and techniques for that, but those people aren't the target audience for this device.
I have no idea if this thing is legit or not, but calling it a scam because accurate non-invasive glucose measurement is a holy grail is completely missing the point of what the device is and what it's for.
There was even a glucose watch available on the market for several years in the US. It was pulled a few years ago, but the basic idea was sound. I do remember the device causing semi-serious skin irritation in many people though.