I like Joshua's last point (#4) related to privacy. It seems like a lot of the "check-in" platforms currently rely on specific points - locations - to check in. This presents a problem because doing so (if done in real time, and if done honestly) discloses your exact whereabouts. In contrast, companies like mine (Maponics) create predefined geofences like neighborhood boundaries so that users can check in to a local area, without disclosing exact location.