Perhaps you mean devices like those described here?
http://www.pac-safe.com/www/index.php?_room=3
The usual problem of TSA wanting to look inside without you being present to let them use the key applies. The company selling the devices has the following on its web site:
Originally Posted by PacSafe
If travelling to/from/within the United States, we recommend that you leave the PacSafe off your luggage during air transit (or at least wait until it has been inspected and permission has been given to lock your luggage).
Their FAQ is found here:
http://www.pac-safe.com/www/index.ph...tegory_id=8#12
They do offer a TSA-openable lock that can be used, but would you expect the TSA to properly wrap it back up if they opened it and unwrapped it for inspection?