Review of Square Cash: The Money Is in the Email - WSJ.com

Another good reason to secure your devices and service subscriptions

"But starting Tuesday, you can just email cash, free of charge, directly from your debit card to anyone else's, regardless of what bank each party uses. There's no login or password to remember and no special software or hardware required—you just use email. It works on both ends using any email service or program on any email-capable device, whether a computer, a smartphone or a tablet.
This new service, called Square Cash, comes from Square Inc., best known for equipping small brick-and-mortar merchants with smartphone-swiping devices that allow them to accept credit cards, and with tablets that act as sophisticated cash registers."

Review of Square Cash: The Money Is in the Email - WSJ.com