Im thinking like an micro chip implanted in our body. This system is not out of the picture because how we discover things every year, it is not impossible that in the future this things may happen and it will boom like btc.
This is a far vision,and i thinks theres a possible in the future thats its can be done,otherwise this is a future vision if this would be implemented soon,but if this would happen thats like a micro chip implanted in our body ,its become in human and not civilized ways and people would againts this kind of system.