Look at this beat wartime empathy device by Dominic Muren. As he explained me in his email:

"Though it's not the most traditional interface design, I feel more and more that really functional interfaces in our world of mediation, will need to be physical. And what more complicated topic to give physicality than war, and the civilian relationship to it. The Beat wartime empathy device is actually a pair of dogtag-like receiver and transmitter, one worn by a soldier, and the other anonymously "adopted" by a civilian. The soldier's heartbeat is recorded, and transmitted, real time, to the civilian, where it is physically thumped against their chest, another heartbeat next to theirs. They feel the soldier's fear, calm, or, god forbid, death. With such an intimate connection, it takes a hard heart indeed to ignore the true cost of war."

Why do I blog this? an intriguing project about mediating physiological cues. I like the idea of a very simple sign (heart beat) being conveyed to connect people.