Boundaries?

In the context of our discussion on speed cameras, government-controlled vehicle controls, and the like, Russell said:

If the law itself is questionable, change the law. But providing law enforcement the ability to, strangely, enforce laws rather than simply responding to them having already been broken seems logical enought to me...

Okay, fair enough. However, that seems like a rather broad statement. What are it's boundaries, or does it have any? Would Russell support, on the same principle, oh... the implantation of coded transponders in all citizens to allow law enforcement to enforce immigration laws? Routine monitoring of phone conversations to allow law enforcement to enforce federal campaign finance, telemarketing, and anti-terrorism laws? Camera's and microphones in people's homes to listen for evidence that they have committed a crime?

Some of these things might be considered unconstitutional under existing Supreme Court doctrine, of course—but current doctrine also allows the Constitution to evolves to meet the needs of the majority of the court without being amended, and I'm pretty sure you could find five judges somwhere that would sign off on the necessary reinterpretation.

So. Is there some point at which that a measure allowing law enforcement the ability to enforce laws rather than simply responding to them is no longer sufficient to justify its implementation?