You and your colleagues have a cash register for beverages in office or club ? Tired of paying with coins ? Why don't use cheap RFID-Tags All you need is a cheap tablet that can do USB-OTG, a card-reader and some tokens Looks good on tablets bigger or equal 7" (Sorry didn't optimize it for smaller screens, when I wrote it long time ago) The first token you read in will become the Matmin-Token, that can change the price and shows the status of the cash register