My city has been using RFID cards for public transport (bus, ferry, metro, train) since 1999. It also is used for access to the International Fair. Credit is loaded at shops or machines throughout the city.
Shops or vending machines could co-operate with the transport network providers to accept the card for low value payments. I think this would work best for fixed price items to give fast transactions.
- More Info:
- Izmir Kentkart - Wikipedia