This is probably interesting.  Hopefully it won't cause cancer... 

http://www.sciencealert.com/forget-bluetooth-new-wireless-technology-uses-your-body-to-transmit-data

QuoteAnother advantage of the technology could be security. Compared to something like Bluetooth, which transmits data in a wide radius of several metres, magnetic field human body communication prevents any kind of digital eavesdropping, as the signals are largely contained to your body. The researchers say information is neither radiated off your body, nor can it be transmitted from one person to another.

While this means the method won't be suitable for sending data from wearable devices to remote gadgets (such as audio speakers or a computer), for personalised applications, some people may find the limitation is actually a positive. "Increased privacy is desirable when you're using your wearable devices to transmit information about your health," said Jiwoong Park, first author of the study.

Sounds like the body becomes the transmitter between 2 items in direct contact with, or maybe close proximity to, the body (like a smart watch and a phone), but no farther than that?