1. A method comprising: recording a first location of a mobile device; determining, by one or more processors of a geographic-positioning component of the mobile device, on a periodic basis, a current location of the mobile device; determining, by the processors of the geographic-positioning component, whether the current location is outside a geographic region defined at least in part by the first location; and if the current location is outside the geographic region, then transmitting, by the processors of the geographic-positioning component, a message to one or more other processors of the mobile device, the message causing one or more of the other processors to transition from a sleep state to an active state.