A set of tracking devices can be placed within a geographic area as part of a scavenger hunt. A user with a mobile device can traverse the area, and when the user moves within a threshold proximity or communicative range of a tracking device, the mobile device can receive a communication from the tracking device identifying the tracking device. In response to determining that the tracking device is part of the set of tracking devices and thus part of the scavenger hunt, the mobile device can modify a tracking device interface displaying a representation of the tracking device to indicate that the tracking device has been found. In response to each tracking device being found, the mobile device can modify the tracking device interface to indicate that the scavenger hunt has been completed.