GPS Bullets and the Fourth Amendment

The BBC reports that police in several states, including my home state of Iowa, are using "GPS bullets":

The bullet is designed to make high-speed chases safer - enabling the authorities to track suspects without having to risk theirs or others' lives. 

And in true spy fashion the system works by hitting a button inside a police car. 

That triggers a lid to pop up releasing a bullet that shoots out and sticks to the car in front.

In United States v. Jones, the Supreme Court held that attaching a GPS device to a vehicle and monitoring its movements was a search under the Fourth Amendment even though the observations could all have been made by simply following and observing the vehicle's public movements.  The tactic was a search because it involved a trespass upon the defendant's property.

One possible critique of drawing direct analogies to Jones facts is that the case only dealt with a GPS device on a car, leaving courts and prosecutors with room to interpret the trespass rationale in other cases.  Police use of GPS devices to track cars seems to be a fairly specific factual scenario.

But as this technological development illustrates, however, the use of GPS devices may be getting easier for police.  While shooting a GPS bullet during a high speed chase would likely be lawful due to exigent circumstances, the vehicle exception, or some other rationale, that bullet's attachment to the vehicle would still probably constitute a trespass-based search, and widespread use of these bullets could raise numerous, interesting Fourth Amendment questions.

As a disclaimer, the BBC also reports that it costs $5,000 to install a GPS bullet system, and each of these GPS bullets costs $500.  This may hinder truly widespread use of these bullets until technological advancement makes them easier to purchase.