"Where do you draw the line?"
As so often, this is the kicker. Already mentioned here is active vs. passive, but even that can become convoluted. Say, sticking a camera on a tree isn't exactly /passive/ even if you deem the thing recording to be so. If you have to trespass to give it a good view or even just a suitable place to hang out, that's another problem. Even "staring" from public property onto someone's private property by electronic device, even if it's otherwise small and inconspicuous, that can easily be unreasonable. So we're back at square one. Where to draw the line?
From the point of view that police, or any government agent, shouldn't have it too easy; they have to /work/ to get into your face, which is sort-of the point of the American Constitution, you could turn it all on its head and say that because obviously any electronics make agents lazy, they require a warrant. If you want to spy without a warrant, go out and stake-out yourself, in person. That suddenly puts a whole different face on the matter: Your victi^Wtargets have a sporting chance to spot you.
Another extreme view would be that anything they can attach to (but not actually modify) cars, houses, telephone wires, trees, whatever, might be fair game. But in return, you might say, any counter-devices might be fair game. Do we want to "weaponise" our society?
I think trying to shoehorn this into a constitutional question is, as so often, a bit forced. Getting dangerously closely comparable to high priests trying to match the latest of technology's advancements to gospel written thousands of years ago. Maybe it's easier to decide just what you want and make a law (or even another amendment) to clarify how electronics use maps onto that protection against "unreasonable" search. Because, just what is this "reasonable" you speak of?
Personally I favour recognising that society is about humans, and not about the technology we make, and cost of putting men on the street be damned. Nevermind that those goverment issue apparatuses aren't exactly cheap either. There's too much security theatre going on already; cut all that and suddenly there's seas of budget to go after perpetrators of actual crimes causing real, demonstratable harm.