Think about GPS-enriched postcards. I'm traveling, I come to a really cool spot, and want to share with friends and family. I take a picture, and along with that is captured the coordinates along with other relevant metadata. I then send it out.

When a recipient opens the postcard, the client app digs into the accounts the recipient has opened access to (default airlines, hotel chains, personal schedule) and builds a potential travel plan. The client app would also pull in special events and deals surrounding the postcard's coordinates, finding slots in the recipient's schedule for those. The originator and/or recipient(s) could network with others to arrange a group travel event.

This would have business applications as well...