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.
People sometimes spend much more time in airports than they'd like to for legitimate, non-interrogative reasons.
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.
