I think you'd still have issues mapping a mesh, especially with how often phones are moving. I remember looking at meshtastic for a mesh wireless network and they're still working on a solution for a large number of nodes covering a large area:
It is only decentralized if the entire world is covered in Apple devices every few meters. At the moment they are simply extensions to a nearby router or cell tower.
https://meshtastic.org/docs/software/other/mesh-alg