Because of the cross-device integration, the watches can do many of the same things as other mobile apps, as well as hand off to other devices. A lot of the notifications offered are similar to Google's Cards.
This is one of the applications I think makes sense for a watch, if you can set it to pop up automatically with no input. That way, you can see your plane status while your hands are busy schlepping luggage.
Though we didn't get to see Samsung Gear -- Google only announced the partnership -- as with the other watches there will be vibration notifications, music app controls, voice reminders, and customized phone-call dismissing.