Not to shoot you guys down here or anything, BUT...

There is already a Federal Case law on thermal imaging that reads...

Kyllo v. United States: 533 U.S. 27 (2001)
Where the government uses a (thermal imaging) device that is not in general public use to explore details of a home that would otherwise be unknowable without physical intrusion, the surveillance is a "search" and is presumptively unreasonable without a warrant.

^ that is right out of the baca book

So I would imagine if anyone were to get "nabbed" doing something illegal by cops using such a device, a even moderately compitent lawyer could shoot that down. And I would imagne some case law would come about focused on x-ray scans. Because if you think about it, its basicly the same concept it just hasn't been put to paper yet, so I wouldn't worry too much about it. Search without probable cause is a search without probable cause.