Sometimes you wake up and you think of a really good idea and then after a couple of hours trying to find out how QR patterns are encoded you remember to Google your idea and find someone's already done it.
But I don't mind. Check out this sweet QR code clock by QR Planet.
In case you're wondering, a QR code is simply a two-dimensional barcode. It's a way of packing a lot of machine-readable data into a small space. QR patterns can encode URLs, text, phone numbers, and contact details. You can scan them with your cameraphone if you have the right software - there's plenty of free programs about to do it. QR patterns encoding URLs typically operate what's known as hard linking - rather than show you the URL encoded, they automatically open your browser and take you to the page. I'll explain why this is important in a second.
I find QR codes really interesting for two reasons. Firstly, they have a huge amount of error-checking built in to them. Unlike a numeric sequence (12345) changing a single bit of data on a QR code can result in an entirely new pattern. Can you imagine if choosing a different word or spelling meant redrafting the entire paragraph? How weird would that be, for a chunk of text to be interlinked in that way?
Secondly, because of this non-modular nature, QR codes are probably impossible for a human to read or recognise. This means they are susceptible to QR bending (see: data bending) or hacking. The smaller a QR pattern is, the less error correction it has, and the easier it will be to take a marker pen and colour in a few extra cells to hijack the code. Imagine activists altering a corporate billboard so that when customers snapped the QR code, they were taken to a YouTube video on climate change instead of an ad for the latest SUV. Because the codes can't be read by humans, it could be a long time before the owners realised the poster had been defaced.
Anyway, just a couple of thoughts.
Nice idea, but unfortunately the code changes so quickly that my barcode scanning app can't keep up!
@ Jacob - TIME WAITS FOR NO MAN MACHINE
Why do you need a cameraphone? Doesn't everyone already know how to read QR codes themselves?
http://burnandbass.com/qrclock/ here is AS3 version ;)