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.
I heard on the news that the microchip implanted in the body had already been tested. I think this is too dangerous for the body, it's better to just use barcode scans on smartphones for every way pay, besides being safer for the body, I think it's more practical too because without implant microchip surgery...