This article from NewScientist.com reports that researchers have been able to transmit data at broadband speeds between two PDA-carrying individuals engaged in a handshake. The system utilizes the conductivity of human skin to transmit a weak electrical signal and would work via any contact, even through clothing.

This is so 'James Bond,' but I wonder if it will have practical applications as well. Perhaps your health status could be passed from your PDA to an EMT's PDA automatically when the EMT comes in contact with you.