According to them, they're tracking Wifi + Bluetooth identifiers.

And yes, for me this means that I've graduated from just putting my phone in airplane mode when I enter a store (to avoid the trackers too many stores have started using) to keeping my phone in airplane mode at all times when I'm not at home.

But whether anyone else should do that depends on how sensitive they are to being tracked.

But I'm thinking that there may be a way to turn my car's body into a faraday cage to block signals from leaving the cabin. That would be a nice compromise.