ask them to register their flight and contact info (twitter, fb email, phone). You monitor their flight for them, if anything is wrong, you tell them with Twil

ask them to register their flight and contact info (twitter, fb email, phone). You monitor their flight for them, if anything is wrong, you tell them with Twilio/twitter/fb, and also send them an ad. Considering it's already a free service from carriers, I don't think you'll be able to do any sign ups.