I think the issue is that the common tech requires sensors in an air-chamber. E.g. NDIR works by firing IR at a frequency that is absorbed by CO2. A sensor on the other side either measures the amount of IR light that got through (optical NDIR) or pressure/sound waves (photoacoustic NDIR). I guess that it's hard to use any existing sensors, because they are relatively large and probably water could easily get into the chamber.
Would be extremely cool if Apple, Samsung, and others can crack this, though I think they'd have done it already if it was easy.
Would be extremely cool if Apple, Samsung, and others can crack this, though I think they'd have done it already if it was easy.