This one is easy,

You take your goods to the checkout - merchant scans them with there normal POS system, the system calculates total and itemised bill / VAT reciept and encodes it into a QR code which is displayed on a cusomer facing screen along with another QR with the payment address of merchant, the customers wallet / payment app on there phone then reads both QR codes and asks the customer for a passowrd or a confirmation to send payment, it can also record the Itemised bill and total for customer records just like a receipt.


so any "peeping tom's" will just see your bill and the merchants address which could also be dynamically created by the POS software if for some reason the merchant wanted to use different addresses.

The actual sending of payment would be done through internet connectivity which is used by merchant POSs' anyway so in rural areas without mobile internet the merchants could provide wifi, could even be built into the POS.