[walterbell]

If present, such implants could be detected with a radio-frequency meter that is logging all measurements 7x24, with post-collection filtering of RF noise on public licensed and unlicensed bands.

If present, such a receiver/transmitter would have needed to co-exist with changes in public cellular radio bands, e.g. the transition from 2G to 3G to 4G LTE over the past twenty years.

[LeonTheremin]

Unlikely to be caught if the measuring instruments themselves are compromised and made to fake data related to that - just like our eyes have blind spots and the brain does some faking.

The effects of sabotage can't be faked - people only need to listen to the victims, because waiting until they themselves are victimized is a losing proposition.

[walterbell]

If consumer-level RF meters were sabotaged to ignore specific bands, expensive professional-level SDRs would be less likely to have the same blind spots, if only because they are used in a wide range of applications by professionals who also have reference equipment for calibration of questionable meters.

If consumer-level RF meters were sabotaged to ignore specific bands, professional-level SDRs could be used to identify those bands. That may be faster and less work than detecting any hypothetical implants, and would itself be a significant discovery of interest to the global engineering community.