[MrB]

Seems to me a scanner of some sort would be in order -

something that would detect GPS and cell phone signals at short range so that you could scan your car for such devices...

[Yo-Yo]

Seems to me a scanner of some sort would be in order -

They make those as well, but most trackers are either passive - they record GPS travels, then the device is retrieved later and the info downloaded - which means nothing is detectable, or they use cell phone technology, which only broadcasts in short bursts infrequently, also very hard to detect with a scanner or spectrum analyzer.

Seems to me the real answer is the 9^th Circus should have ruled that a warrant was required to install any tracking device, just as a warrant is required for a wire tap, a home search, or retrieval of phone or internet records.

Clowns.