There have been several devices like this brought to the market with credible looking web sites (but I used to work in design and making web sites literally sell legitimacy) -- but they turned out to be fake and over sold and underdelivered and scams.
But I'll send this over to someone I know who works high up in the tech world and have him investigate. If it really can track my muscle O2 Saturation and Lactate build up I'm buying it.
If it really worked it would be phenomenal. That said I still follow loads of runners and professional athletes and have never heard of this device and no one I know trains with it which is a red flag for me, a lot of runners like to crunch their numbers, keep Strava public records and follow others Strava profiles etc. It's a geeky crowd.
I was thinking more about these devices last night. To me it seems that accurate measurement of body functions isn't the primary function: it's providing some numbers in a convenient and fashionable way. Measuring heart rate accurately is easy...if you use inconvenient stick-on electrodes. The Humon sounds like another fashion accessory and addition to bragging or competition on social networking. Maybe it--and other such devices--are of actual value to some people, but I expect the majority will be sold as fashion accessories or yet another gadget bought 'to lose weight or boost fitness' and ignored once the owner realized that it still requires effort and willpower.
I looked at both the articles you cited. The second one states that fitness trackers like Fitbit are surprisingly accurate as to heart rate, but fail abysmally as to energy expenditure. However, from what I can tell, Fitbit and related devices measure energy expenditure (calories expended) in this way:
The calorie burn estimate that Fitbit provides takes into account your BMR, the activity recorded by your tracker, and any activities you log manually.
This has nothing to do with using near infrared light to measure a muscle's hemoglobin saturation and then calculating muscle oxygenation as the Humon Hex does, as described in the first article you cited. Using near infrared light in this way is similar to how pulse oximeters work. Actually, now I'm wondering how the Humon Hex differs from a pulse oximeter! I've used a pulse oximeter in the past when crashed, thinking it might show low blood oxygen levels, but no such luck. Mine was always fine. And I tried it after climbing a flight of stairs, but again my oxygen level was fine.