Use GPS and cell tower tracking to determine if you are inside an airport. If you are inside for longer than X minutes, send a message to selected people stating that.
Perhaps take into account authenticated activity, or lack thereof? Activate this special functionality when you anticipate possible issues (e.g. going through airport security) and you've got a timer waiting on some element from Action Set Y to occur every X minutes before notifying emergency contact(s) Z, specified previously.
Sounds like an idea...