Updated Feb, 10th 2013
The AGRA would provide a missing-link between the GPS system and the cell-system. Users would install it, and it would run in the background - the user never needs to do a thing. It provides location information which is totally anonymized – it is in no way associated with a specific device.
The power in the system is derived from data-mining which is able to aggregate and recognize traffic patterns across time, and then compare current feedback so as to determine the delta between average usage and current usage. This is then translated into feedback which is disseminated via regular GPS apps.
(Even as I write this, though, I feel like this has already been done! Hmmm... Wish I knew more about the tech underpinnings of GPS. And the cellular system...)