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.
These kinds of payments are scary I've seen a video where a man just buying something from a machine, then a man at his back approached a reader on his wallet and voila! payment received!
It's really nice to innovate but I hope we know what is it we are going to use or even where it came from and why. Sometimes technology brings to bad rather than good.