We have this in The Netherlands for quite some time already. It was introduced in 1996.
All our bank cards are equiped with a chip and that chip has some memory.

On special loading stations (usually right next to an ATM), one can load "cash" onto your card.

For that, you require your personal and secret Personal Identification Number (PIN). For security reasons, one can not load more than 500 euro on the card. When stolen or lost, that amount of money is lost. Since a loaded card can be used to pay without use of a PIN, anyonme can use that card.

In a store, or in a phone boot, xerox machines in stores, vending machines, or when you need to pay for parking, you insert your card in a little machine and the amount to be taken from your card is shown in a display. You only need to press the "YES" button and you've payed. Takes just 2 or 3 seconds. The amount you've payed is immediately subtracted form the amount on the card.
They're also widely used in sidewalk cafe's. No more hasle with cash, the waiter/waitress enterd the amount, you insert your card and press "YES" and you're done.
I think it's a neat and convenient system. I never put much money on it, just as I would never cary a lot of cash with me.
Since 2 years, that chip is also used for something else. It's no longer allowed here to buy tobacco products here when younger than 16 years old.
In a regular store, the seller can verify the age of the buyer, but with vending machines that's a little tricky. And since vending machines are used a lot here, for sellign cigaterres, something had to be found.

A system is developed that uses the same chip on a bank card. A special code, the Age Key, must be written in that chip and when that code is not present, the vending machine will not accept the payment. To get that code in your chip, you need to go to your bank, with a passport or other official ID with photograph that states your age. On these vending machines, purchases require a PIN, so it's unlikely that a too young person will use the bank card of an older person, as reveiling the sectret PIN is not likely to happen.