The relative positions of two or more electronic devices can be determined utilizing ultrasonic beacons. Each device can have a unique signature that can be included in the beacon broadcast by that device. A device having an array of ultrasonic detectors can receive a beacon and correlate the beacon received at each detector. The time of arrival then can be used to determine the relative position of the source of the beacon. The signature in that beacon can also be used to determine the identity of the device that broadcast the beacon, in order to determine the identity of the device, or a user of that device, at the determined relative position. The devices can be configured to transmit signals over the air or through a specific transmission medium, such as propagating surface. Further, a dedicated detector array can be used for determining multiple relative positions.