Grocery chains / big box stores could add it as part of their rewards points programs.
-> Attach email to safeway card.
-> Scan safeway card.
-> Receive receipts via email.
But this also means replacing hardware, which is a more expensive proposition.
My bank already knows my email address and phone number(s).
I would expect that the easiest way of doing this would be for the banks to handle it all - when I buy something my bank gets a receipt signed by the shop's bank to say that I did buy item X at time Y at location Z. My bank could perhaps then countersign the receipt to link that strongly to my identity.
It would be particularly good if the format included a standard representation of tax paid (VAT etc.) - would make filling out expense claims so much easier.
Actually, shouldn't this be doable entirely in software?
The POS already scans the reward card, the POS talks to a master computer (for inventory reasons), that data gets back to an office which has internet, from which emails could be sent.
But this also means replacing hardware, which is a more expensive proposition.