Measure the impedance across the windshield. And I do have a crack in the windshield but It's not getting bigger.
With what? They're gonna stick motion sensors all over my car? And yet they'll be so craftily hidden I won't be able to screw them up with a piece of Wrigley?! Or maybe they'll use lasers to map out my windshield, and while they're at it it'll map my hands and make sure I'm properly at 10 and 2 (never, I drive a stick, 12 and sometimes 6) and do proper hand-over-hand turning (never, I've mastered the flatpalm grip)?! Not happening.
I have a crack too, it happens to be up where the tint strip is so it's never grown.
Maybe, and this is a big maybe, RFIDs and readers in road signs. Here's always the problem with these things: why in God's name would anybody want all this data? What purpose would it serve? The worst thing that could possibly happen with this is they'd use it to generate speeding tickets (a frequent charge), because then nobody would be able to get away with speeding anymore, and nobody would speed anymore, and the police departments of our land would go broke... hmm now that I think about it maybe these things ARE a good idea ;)