Logitec (not to be confused with Logitech) has just released one of the nicest external drives I’ve ever seen with many features that could interest you.

The drive’s size is 2.5″ and it has a rugged body and mechanism that protects it from falls (up to 1 meter) and allows you to encrypt data, so only a person with the correct program (and correct encryption key I guess/hope) can access it. It’s also laptop friendly because it consumers 50% less energy than the most common external HDDs so it won’t drain your battery as much.