For those who remember BadBIOS, it seems that the advertisement and business in general didn't took long to communicate between different devices using ultra-sonic frequencies.
Imagine a web advertisement talking directly from the web browser on your laptop to the smartphone on your pocket and exchange information about whatever they decide. Doesn't this sound fun?
Read more details at:
http://arstechnica.c...-tablet-and-pc/
How about an app to counter-detect these things?