At a much more basic level, Waze users construct the best map of actual cell phone network coverage than anything the cell phone service providers have. So, it was seem reasonable to map coverage based on where the app loses connection and when it returns. This could be used to preload for the "dark" areas, just warn the driver that they are about to lose connection (useful when determining if a voice call is going to drop), and it might be nice in the case of route planning to pick the route with the best network connectivity.
At a much more basic level, Waze users construct the best map of actual cell phone network coverage than anything the cell phone service providers have. So, it was seem reasonable to map coverage based on where the app loses connection and when it returns. This could be used to preload for the "dark" areas, just warn the driver that they are about to lose connection (useful when determining if a voice call is going to drop), and it might be nice in the case of route planning to pick the route with the best network connectivity.