My new BMW has a key "fob" that acts as a transponder when you want to open doors, start engine, etc. I don't plan to check it as they are quite expensive to replace (not to mention the issue of what to do when you arrive at your home airport and your luggage does not). I would imagine that many people in Washington also have vehicles that use similar keys, so I seriously doubt that the US will be adopting this idiotic rule. It makes no sense unless you ban all electronics (which is also nonsensical) as most bombs in the middle east are set off by cellphones, not keyfobs.