Something I came across.

When traveling with equipment such as firearm, audio-visual, or camera cases you need extra security when checking it with the airlines.

The SearchAlert TSA Heavy Duty Case Lock is the only TSA approved heavy duty travel lock on the market which is specifically designed for air travel with firearm or other equipment cases. This heavy duty case lock alerts you with the patented green light/red light window if your lock (and case) were opened by the TSA.