Why not go further with the idea of a Travel Mode toggle and have it be tied to the device itself. This cuts out any possibility of any data being left on the device from being analyzed easily, social media or otherwise.

Google and/or Apple could add this as a new menu toggle similar to Airplane mode. Once switched on, while in an airport, prevents the device from being unlocked. Then by utilizing geofencing, once the device leaves the airport it unlocks and can be used again.