This is a fantastic story: "Rather than using a standard punch card or signing in electronically, the clock presents a QR code that the users snaps a photo of -- designating the times at which they check in or check out."

Not so much for the idea of using QR codes as a punch-in clock; like the article says, that's pretty pointless. But it had never occurred to me to change barcodes from being static items to dynamic things that change over time or in response to the environment...