In KYLLO v. UNITED STATES ( No. 99-8508 ) I think it can be said that what does and doesn't fall under a fourth amendment protection can be so convoluted as to be almost impossible to determine.
http://www.law.cornell.edu/supremecourt/text/99-8508
When you think about it, it appears that our bill of rights as guaranteed under the constitution can be subject to reinterpretation under future supreme court rulings and nothing is guaranteed.