An apparatus is provided that includes an input system, an output system, and a sensor for sensing magnetic fields. In one example, a signal processing circuit electrically connects the input system to the output system, and a magnetic sensor adapted to inhibit the acoustic input and function as a magnetic input in the presence of a magnetic field. In one example, the magnetic sensor includes a giant magneto resistive (GMR) sensor. In another example, the magnetic sensor includes an anisotropic magneto resistive (AMR) sensor. The magnetic field can be generated by, among other things, a magnet in a telephone handset. The hearing aid further is programmed based on time-varying characteristics of the magnetic field. Wireless activation or deactivation of the hearing aid is also described. Other examples and options are provided herein.