Even though we fully acknowledge our unusual paranoia about anything involving airport security, we think normal people may benefit from something like this too.
The "Bag Snatcher Alarm" might be worth the $72 investment if you've ever had a momentary panic attack when separated from your luggage at a terminal counter or hotel lobby, however briefly. The concept is simple: You attach a signal transmitter to your suitcase or bag, then affix the receiver to your keychain, clothing or forehead. If the two devices are ever separated by more than 2 to 5 meters, the receiver will emit a loud beep. (Just pray that there aren't any trigger-happy security guards in the immediate vicinity.)
For items that you're willing to let stray more than a few feet away--like whining kids--you may want to consider the "Loc8tor."