SpotEx is a new indoor positioning service that uses Wi-Fi access points to deliver targeted messages to mobile users. It builds an expert system of rules that define when certain user-generated messages should be delivered based on a user's proximity to specific Wi-Fi networks. The system includes a database to store these rules, a rule editor, and mobile apps that can detect nearby Wi-Fi networks and execute rules to deliver messages if conditions are met. Future development may include a WiFi chat feature to enable local discussions and forums associated with Wi-Fi access points.