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.
Bitcoin is the present and future payment i think. Anything is being developed goes in a deep evaluation if it is good to humanity or not. We always think for the effect of to humanity. If we embed something into our body the radiation will not be god for our health, and also it will be like a clothing from a mall that has a RFID chip, we will be compared to those things.