FYI: Kingston DataTraveler DTLocker+ is a USB key with 100% hardware-based AES-256 encryption and enforced password protection. If stolen, it will erase and reformat the contents after 10 failed password attempts.

The disadvantage is that you have to be coherent to tell someone how to access the data. A trade-off in emergency situations, but perhaps one you might consider. My company uses these and the more expensive, enterprise-focused SanDisk hardware-encrypted USB sticks and they work flawlessly.