So, what about a P2P network using bluetooth to communicate traffic information between cars on a highway? Imagine I'm in a car going South on I35. On my dash is display of the road conditions for thirty miles around. How is this produced?

It's produced by my car talking to the other cars as they pass on this side and the other side of the road. As cars pass me in both directions my car communicates to them the conditions I'm currently experiencing, that is how fast I'm going, where I am now, and a trail of my speed and location over the past thirty minutes. It also passes on data it has received from other cars in the past thirty minutes. The cars that my car provides data to reciprocate, and transfer their data, and data they've collected from others, to me.

Cars coming towards me, going North on the other side of the road, can provide information about conditions ahead of me. They've collected this from cars in front of me when they passed them a few minutes ago. The data I provide will be useful to cars behind me; it will be transferred to them by the cars that pass me going North. As cars enter and leave roads the data is spread out so that it's likely that I'll know the conditions down each turnoff that I pass. Certainly I'll be aware of conditions on any road with heavy traffic. In this way each car can maintain on it's own, with no central authority or monitoring, a picture of the road conditions around it based on information provided to it by other cars.