As far as |3lack|ce's scenarios:
For the inventory searches of impounded vehicles, ( see COLORADO v. BERTINE ), there are some requirements which might have to be meet before being permissible ( as an example, see FLORDIA v. WELLS ).
and

You might want to check out DELAWARE v. PROUSE about restrictions that may apply.
Teach ME to discuss law without Mrs|ce present :P Thanks for the precedents on those, I'll look 'em up in westlaw.