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.
Yeah it might happen in the future because technology always goes forward right, but I still can't imagine what kind of payment method
will happen because our knowledge is still limited by the current time and current technology ? so I can't imagine what kind of technology will be