Americans soon might head out of the house holding car keys, mobile phone and a digital wallet. Welcome to the world of cryptocurrency.

 

Only a few months ago, Memphis entrepreneur Philipp von Holtzendorff-Fehling attended a convention in Miami. He said it helped him glimpse into the future of money.

“I’ve always been interested in the next thing happening to humanity,” said von Holtzendorff-Fehling, a former marketing chief for Memphis-based ServiceMaster. “This is one of the next big things.”

He had come across Byte Federal, a little tech startup from Venice, Florida.

Today, one of Byte’s automated teller machines stands outside von…