CurrentC - which is an initiative spearheaded by Walmart. Unlike Apple Pay which uses NFC, CurrentC uses the good old QR code scanning technique, which should in theory make it ubiquitous. But it's not happened so far.
Wouldn't that depend on the customers phone having a data connection? You need 2 way communication to produce a secure payment protocol.
The goal isn't to be secure. As far as I understand it would basically be similar to Starbuck's current mobile payment service, where the scanner reads the code which maps directly to an account and processes the transaction. No two way communication.