I don't know about checked baggage, but a lot of airports now have the bomb detection machines that they use on laptops. I first saw them here when I was in Charlotte last Thanksgiving, but since then I've seen them in National and New Orleans also.

The main problem is that of the 20 or so times that I've gone through a checkpoint with the said machines, they've only checked my laptop once, and that was the very first time I saw the machine in Charlotte.