Starbucks Card

Though I hate to say it, it's an impressive system. You get a card (any card) and then top it up with cash. You can then use the card in stores in the UK and abroad and use them to buy stuff from Starbucks.

You can also register the card on the Starbucks website (and it then becomes a loyalty card and they're meant to offer freebies etc - though as it has just launched, yet to be seen). When you register the card, the card balance and what you've spent show up on the site. What's amazing is how quickly. Having bought a coffee the transaction showed up on the site within 10 minutes (the time taken walking from the store home).

Another way for Big Brother to track you, but as long as they give free coffee you can stay awake thinking about everyone spying on you.