I've never put my wallet through the xray machine. I'd be afraid of someone snatching it at the other end, while I'm hopping around trying to put my uber-dangerous shoes back on.
Can't say that the SD cards would set off the machine. I doubt it, though, but like it's already been said, it depends on the airport. Last time I flew from here, I forgot to take my belt off, and the combination of my glasses frames and the belt buckle didn't set it off. Sometimes they crank the sensitivity way up, and pretty much no one gets through without setting it off.
Make sure you take off your watch (if it's metal) and empty your pockets of other metal items (nail clippers, loose change....not supposed to set it off, but why take the chance?.....keys, etc). Then you'll barely have any metal on you, and you're sure to sail through.
Now if they'd only get the rest of the people going through security to figure that out......
