Similar to a bar code a QR code works along with a number of free applications you can get for your smart phone. They’ve been using this technology in Japan for a few years and it’s starting to grow here in the US. A lot of people are hesitant to begin using these but I’m positive that the use will grow. You really have nothing to lose because you can generate them in a matter of seconds and they are free. You can even generate a custom one but it’s not really recommended because  they don’t always read well.