from the literally-subliminal dept.
Anemophilous Coward writes "ZDNet has the following article which describes a company that 'has devised a method for sending wireless signals over ordinary audio speakers so that humans can't hear them. With this same technology, radio stations can unobtrusively transmit ads, Web site URLs, or information about music and artists to in-car cell phones.'" Here is some further reading about the company, Intrasonics.
I tell them to turn to the study of mathematics, for it is only there that
they might escape the lusts of the flesh.
-- Thomas Mann, "The Magic Mountain"