If you’re ready to think about doing the fedex, you’re already in the highly prepared minority. The real solution is something that takes minimal thought. The cell phone approach is good because it’s also a great anti-theft. If you turn on the laptop in the presence of your enabled bluetooth device, it just works like now. If you turn it on without that device on and nearby, it can’t access your encrypted data.

The goal here is that this isn’t very common, so customs doesn’t know to demand your laptop and your phone, or your laptop and your bluetooth key fob. Which gives you a short time in which to execute the command on your phone or fob to erase the key.

Indeed, you could even get to the point where, if the laptop is running, the command from the phone via bluetooth tells it to erase the key and shut down. However, it is an open question if this is obstruction of justice or not.

The main point is most people — this is for innocent people after all — will not remember to follow any special procedures before they get into customs. If they can legally follow a procedure after they get into customs, or after their laptop is taken, that’s what works. The same applies to theft.

Note that this requires a phone that is always on and ready for bluetooth whenever you turn on your PC. Not all phones are that way, but many are.