Apple has patented a technique to hide sensors beneath the skin of a product. They will be completely invisible and undiscernible any other way as well (in direct contravention of 1194.23(k)(1) of Section 508, which is now under review). But embedded LEDs may announce their presence via patterns of micro-holes drilled by frickin’ lasers.
We love seamless input devices, we really do. We’re sleek as seals ourselves. But unless there is some redundant alternative or accessibility technique, blind and low vision users are going to be excluded.