That said, there is the reality of radio signals.

Even with perfect app isolation, a smartphone is still a radio device. It continuously negotiates with cell towers, and those signals alone allow coarse location and movement inference via triangulation. No phone number is required for this—an active cellular modem is enough.

Cell tower data sits with carriers, and accessing it typically requires law enforcement involvement—warrants, subpoenas, or lawful requests depending on jurisdiction. That's a different threat model than app-level surveillance, which operates without legal process. But the data exists, and it's accessible to anyone with the legal authority to obtain it.

Wi-Fi and Bluetooth expand that surface further. Probe requests, MAC behavior, and proximity signals can be used to infer presence and movement relative to known access points or other devices, even when not actively connected. Modern OS randomization helps, but it doesn't eliminate correlation, especially over time.

A dedicated device without a SIM reduces exposure, but it doesn't make the device invisible. A cellular-capable phone still participates in radio ecosystems unless radios are disabled entirely. Airplane mode with selective re-enablement, Wi-Fi-only play, or a data-only SIM with no voice number can reduce linkage, but none of these defeat physics.

The takeaway is the same principle as before: this isn’t about achieving invisibility. It’s about bounding risk—using isolation and compartmentalization to limit how radio-derived location signals can be tied back to you and what else they can touch.

For higher-sensitivity threat models, that can even include keeping the device powered off in a Faraday bag and only removing and turning it on once you’re already in a location that’s acceptable for exposure. It doesn’t defeat physics, but it prevents transitional movement data from ever being generated.