One of the best features of the new class of U.S. mobile smartphones is that they're finally capable of reading QR (Quick Response) codes. These codes, which already appear all over Japan and Korea, are 2D bar codes typically displayed on something -- such as a poster, webpage, magazine ad, or store window -- and captured by a phone camera. The phone decodes the image and launches the appropriate application to see the text, browse the website, send SMS, or call the number that was contained in the QR code. In all these scenarios, the phone is reading the QR code. But you can also turn this model on its head by having the phone display the code to be read by another device.