BitCoin and other crypto-currencies are gaining popularity at the moment - but I remain firmly convinced that they're too hard for the average person to use. I have, however, watched with interest as an ecosystem grows around them.
In particular, I like the way The Pirate Bay (and others) have used QR codes to facilitate easy payments and donations.
The QR codes contain only three variables - the payment method (BitCoin), the destination, and a message. As this is a donation there is no value set. There is a full specification for a BitCoin URI scheme which I think is fairly well designed.
I envisage a day when, on asking for the bill at a restaurant, I am presented with a paper slip totting up my purchases with a neat QR code printed at the bottom. Scanning the code will pull up my banking or credit card app and allow me to make a payment. A verifiable receipt is either shown on screen or sent directly to the restaurant.
PAY: WHO:Pizza Palace IBAN:GB29NWBK60161331926819 CUR:EUR VAL:27.35 REF:123456qwerty TIME:1370886496
That's enough human readable information - and machine data - to ensure the correct payment gets from one person to another. I'm sure there are some other fields which may be advantageous to add; tax rate, specific location, etc. But it certainly all fit within a QR code.
QR codes can easily be printed out using the current infrastructure of mobile POS terminals. Those terminals already have mobile network access so can be alerted in real-time when the payment is made. IBAN means we have an easy(ish) way to uniquely identify payment destinations. And, in the UK at least, we have a fairly rapid payments infrastructure.
What's needed is a simple standard and mobile banking and credit card apps to support it.