Brandon Wiley invented an ATM machine this week for complementary currency using QR codes. Writing python code on Google App Engine, he wrote code which can generate a QR code using Google Chart API and an oauth consumer to allow someone to redeem the currency without giving the ATM site the username and password to their account. The transaction was made with the OSCurrency API. Some more API support needs to be done to make the transaction more resistant to counterfeiting, but it already makes a cool demo.