Electronic sales receipt via wifi transmission to mobile phone

Imagine using NFC and a universal mobile app setting up Wifi channel with cashiers and transmitting sales receipts in protected PDF form to smartphones. This can save trees of the world and help relieve fiscal cliff in scale of billions dollars per year. Also better cash/consumption/receipt management can be made possible with mobile app too. And longer receipt retention period than thermal paper can also be achieved. To enable this technology, relevant IT sector, hardware/software markets and developer manpower will be activated and boosted. That process revolution can be analogous to the advent of digital photography.