Idea popped into my head: You have an app on your phone. The wifi and cell signals go dead and you're in the middle of a protest. You do that, you look around and, "Dude, your phone working?" The shake then initiates an instant negotiation with the phones around it, and this spreads out until all such devices in the whole area are talking through short beam messages.
I think they are capable of this. I'm not sure. Exploitable probably so...