Hearing the Unseen has evolved into an iphone game and generative music machine called Ear Trading. It is now ready for beta testing after which it will be released as on the iTunes store as a free application.
The website for Ear Trading is http://eartrading.moon.net.au
If you are interested in beta testing the application, please send your iPhone UDID (Unique Device Identifier) to firstname.lastname@example.org. (update: EarTrading was released in the iTunes store in August 2010 but was removed a few years later when new versions of iOS stopped it working)
Note: To find your UDID, open up your phone in iTunes, click on your serial number (it should change to your UDID), then copy the UDID (using Edit > Copy or pressing Cmd/Ctrl-C)