The article fails to mention that most smartphone mic and earpiece/speakerphone audio paths are usually controlled by the baseband processor, as well as, of course, the 3G/4G mobile radio. In other words, there's an autonomous phone in your phone, with sufficient peripherals to be turned on based on a special command from the mobile network, and to work as a room bug. This was revealed in an FBI mob case where such room bug evidence was used.