Example methods and apparatus to detect mobile devices are disclosed. A disclosed example apparatus includes a processor and a memory in communication with the processor having instructions stored thereon that, when executed, cause the processor to determine whether a first wireless transceiver is in communication range of a vehicle. The first wireless transceiver is to provide an identifier associated with a person. When the first wireless transceiver is not in communication range of the vehicle, a second wireless transceiver in the vehicle is transitioned from a first power transmission mode to a relatively lower power transmission mode.