This paper by Mike Bond Steven J. Murdoch and Jolyon Clulow from the Computer Laboratory at the University of Cambridge, was published a while back and even made it to the BBC News site. Steven was on my course at Glasgow.
Since I recently received one of the PIN letters using Hydalam's technology, I thought I'd have a go using Photoshop CS2. I scanned in the PIN section using my flat bed scanner at 2400dpi and 48 bit colour and saved as a TIFF, loaded in Photoshop and followed their instructions reasonably closely. The threshold I found was the most important function, Gaussian blur helped to make it more readable and a tweak of the levels producing quite amazing results. Whilst I didn't get the whole PIN I got 2 of the numbers correct, 1 was a similar glyph and the last was plain wrong.
I'm sure a few more attempts with the scanner and Photoshop and I would have probably got the whole number.
Interesting experiment and quite surprising that this was possible using a 50 pound scanner!