In addition to facebook, it would be helpful to have twitter, linkedin, etc involved. Also, if I belong to meetup, figure out what groups I like where I am and show me the meetups / events that are happening where I will be.
I don't travel enough for this to be interesting, but it could be for sales people who travel quite frequently for their jobs.
As a tangent, you could make a service called whom else should I sell to there... If I am going to make a sales call in san francisco, tell me what other companies with offices there I can call on as well.