A quick new thought about GPS tracking.
A recent article about military GPS devices mentioned that they had anti-jamming capability. This caused me to poke around the Internet a bit, and I discovered that there is a growing market in civilian GPS jamming devices. A good example is this UK company. A good summary of why these devices pose risks is here.
First thing to know: use of the devices are illegal under U.S. law. Unlike radar detectors, for example, the devices transmit a signal, which means they are covered by the FCC and various Federal laws. Foxnews has a decent article about the issue here. Here is the most important paragraph:
[T]hey're unquestionably illegal to buy and use in the United States. The FCC is bullish about pursuing anyone who buys a GPS jammer and will prosecute and jail anyone who uses one. Yet they're easily bought online, and their proponents say they should stay that way. Fox News was able to buy GPS jammers for as little as $50 from numerous online sources.
What to make of this from a Fourth Amendment standpoint. Two initial undeveloped thoughts:
First, the growing market for these devices is some evidence the privacy interest in the information gathered by a GPS tracking device is well understood and significant.
Second, the use of these devices by a criminal is likely to backfire. I think that if law enforcement put a device on a vehicle (with or without a warrant), and then it became obvious the device was being jammed, that provides probable cause to search the vehicle to find the illegal device.
(My original post on the issue is here, but check out the archive for lots of information on this issue.)