In one arrangement, a first user sends information from a portable device and receives a response that depends, at least in part, on the location of a second user's portable device. The information sent from the first portable device may be based on data captured by a sensor in that device. In another arrangement, a user of a portable device sends two types of data, sensor-related data and location-related data, and receives a response that is based on both of these of data. In one particular such embodiment, the user scans a barcode or watermark from a coupon or other printed object, and sends decoded payload data—together with location data (e.g., GPS data)—to a remote server. The remote server routes the information to a vendor near the user who can, e.g., fulfill an order for food delivery to the user.