[Misiur]

http://smus.com/ultrasonic-networking/ - from what I've read it'd have to be some kind of realtek chipset 0day to send the message, I have no clue about receiving stuff though.

There is no confirmation whether the whole badbios it's hoax or not (kind of bigfoot), but alternative communication methods are real fun - for example using computer leds (maybe hard drive activity indicator) to send information, and webcams to fetch it is cool.