Thomas Amberg just told me that Kaywa's QR Code solution is mentioned in the new O'Reilly book Making Things Talk. I wait for a scan of the page now;).

PS:
We were also mentioned in the german magazine acquisa, Das Magazin für Marketing und Vertrieb. Next to the article about QR Codes, the Staatstheater Darmstadt-Kaywa example is mentioned particularly. Thanks Philipp!

Also lately we were in konsumTV magazine, following up to the television report about Kaywa and QR Codes.