Re: "Offloading positioning to the devices makes it . . ."
I can't wait till another group of researchers uses this to prove that you can mess the positioning up enough to cause navigation systems to mess up. I assume it won't actually happen, but just imagine a ton of evil devices on a road all sending out their actual location shifted left by five meters.
Satnav: "You need to be in the right lane now."
Driver: I think I'm already there.
Satnav: Move to the right.
Driver (requires brain cell shortage, so we know that won't be a problem): *drives into lake*
Satnav: "You need to move even more to the right now. You need to be in the right lane for this next turn."
Although it's actually more likely that people use this mechanism to crash drones.