The contents of a briefcase - a disaster waiting to happen?

Recently a good friend of mine who is an appraiser, had his car stolen while stopping at a mall to pick something up on his way home from work. His briefcase and digital camera were in the car. The car was recovered just a few blocks away - minus the briefcase and camera, and a few tools and stuff from his trunk.

After talking to him, I got to thinking about some of the "sensitive" information in our clients files that we REALTORS® carry around in our briefcases, and it gave me the chills. I've decided to rethink what I am going to carry around with me in my briefcase. I also think we should treat our briefcases as though they are made of 24 carat gold with a diamond encrusted handle! In other words, we should be VERY careful to not get complacent and leave it in the car for any reason - otherwise it's a potential disaster waiting to happen.

Any suggestions or tips out there as to how we might consider handling this situation?