There are many useful surface electromagnetic (EM) waves for physiological signal detection, for examples ECG, EMG, EEG, and together they are referred to ExG with different magnitudes ranges and characteristics. But people don't refer to them with s initial sECG, sEMG or sEEG because by their very definitions they are belong to surface EM waves category.
> Surface electromyography (sEMG)
EMG[0] require a needle in the muscle, sEMG is an improvement.
[0]: https://www.mayoclinic.org/tests-procedures/emg/about/pac-20...
In hindsight it seemed stupid for meta to invest so much in AR/VR but the techn they release continues to get better.