Techniques for using wireless devices to implement sensor networks are described. For cognitive radio, a wireless device obtains measurements for a first system (e.g., a broadcast system) with which the wireless device is not in communication. The wireless device sends the measurements and associated location information and/or timestamps via a second system (e.g., a cellular system). A server receives measurements from a number of wireless devices and determines the coverage of the first system based on the measurements. For other applications, a wireless device obtains sensor information from at least one sensor at the wireless device and sends the sensor information and associated location information and/or timestamps via a wireless system. A server receives the sensor information and associated information from a number of wireless devices, aggregates the sensor information, and constructs a map. The wireless device may develop a user profile based on the sensor information and associated information.