WIFI broadcasting in a P2P like network
When having problems getting to the network. Waze can WFI brodcast you report and bounce it from client to client until it gets to the server and in the way you just notified all the cars near by that are the once they need the information.
ie. Broadcast an accident you just reported to the cars going on the other direction and just passed near you.
Eduardo Benedicto commented
VANET (Vehicular Ad-Hoc Network)
Android adhoc. Doing some hacking it can be done.
There are many security problems but they can be solved downloading a digital signature from the Waze central servers and use that to encrypt the WIFI network