A paper by Mohammad Eshghi and me on leveraging wireless sensor networks to allow municipalities to provide smartphone navigation services even when internet access, cell phone networks, and even electricity are no longer available. The simulated system allows users not only to reach their goal but most importantly to get there safely avoiding flooded areas and dangerous detours. We estimated a cost of only $12 per sensor node. Sensor nodes are to be installed in the streetlights in the area to be covered. Being installed in streetlights, there is no maintenance cost for battery exchanges.