A tracking system can provide smart alerts based on a user's location. The tracking system can receive a location of a user's mobile device and establish a geographic boundary around the location if the mobile device remains at the location for a threshold amount of time. The tracking system can receive a new location of the mobile device outside of the geographic boundary and configure the mobile device to scan for a tracking device associated with the user for an interval of time. If the tracking system detects the tracking device within the interval, the tracking system stores information indicating that the user possesses the tracking device. Otherwise, the tracking system sends an indication to the mobile device indicating that the user has left behind the tracking device.