I think the more important issue Judge Kozinski brings up in his dissent is the increasing approval of the use of super-human observational powers by the police. The rule used to be that what the police can readily see--literally, see, with their eyes--had no expectation of privacy. Now it's whatever information the police can gather using increasingly unlimited technological means, like GPS trackers, only vaguely related to that standard.
I can't make up my mind about the GPS issue. Like yourself I find it extremely intrusive, and I do have a problem with the idea that they can attach it to your car - are you really 'secure...in your [] effects' under the 4th amendment if the police can mess with your stuff in this fashion?
On the other hand, we accept the reality that the police often stake out suspected criminals to observe where they go,, who they meet etc. So if a police officer was watching someone's house from across the street, watched the resident emerge and drive away in his car, and followed the suspected person with a tail car or a police helicopter, we wouldn't find anything particularly unusual about it; when you're out in public you're subject to being observed by law enforcement as well as everyone else.
So in that sense, the GPS is doing nothing more than automating what would previously have required a team of undercover officers to observe - just another instance of modern technology creep. But it means we now gather information on people where we might not have been willing to commit the resources before unless it was serious enough. And there's the issue of where the the line between observation and interference is.
I agree that this is area of concern for privacy. Right now the general standard on what police can use for technology is that they can use the same technology that is readily available to the general public. It isn't an unlimited-means standard.
Thermo-imaging equipment to detect marijuana growers is not readily available, so it cannot be used.
Telephoto lenses can be bought by anyone, so they can be used.
GPS is readily available, so it can be used.
The standard certainly is a moving target. I don't agree with its wisdom, but that is the law as it stands.
Pinging the location of your cell phone is a capability used by police without a warrant (in some jurisdictions) that is not available to the general public.
Actual dissent: http://www.leagle.com/unsecure/page.htm?shortname=infco20100...