An implant system comprising: an implantable portion (202, 301) including: a battery; a switch for providing power from the battery; and a Hall sensor, wherein the switch is configured to be controlled, at least in part, by output from the Hall sensor; and an external portion including: a first magnet, the magnet for applying a magnetic field to the Hall sensor so as to control the switch; a power signal transmission module for transmitting an electrical power signal across the skin of a user; wherein the implantable portion (202, 301) further includes both a second magnet and a receiver module, the receiver module for receiving the power signal across the skin of the user, wherein when the first magnet is placed in a first position, the external portion is held in place on the user based substantially on the magnetic forces between the first magnet and the second magnet, so as to align the power signal transmission module and the receiver module, and wherein the first magnet is configured to apply a magnetic field to the Hall sensor when in a second position relative to the user, so as to control the switch. an implantable portion (202, 301) including: a battery; a switch for providing power from the battery; and a Hall sensor, wherein the switch is configured to be controlled, at least in part, by output from the Hall sensor; and a battery; a switch for providing power from the battery; and a Hall sensor, wherein the switch is configured to be controlled, at least in part, by output from the Hall sensor; and an external portion including: a first magnet, the magnet for applying a magnetic field to the Hall sensor so as to control the switch; a power signal transmission module for transmitting an electrical power signal across the skin of a user; wherein the implantable portion (202, 301) further includes both a second magnet and a receiver module, the receiver module for receiving the power signal across the skin of the user, wherein when the first magnet is placed in a first position, the external portion is held in place on the user based substantially on the magnetic forces between the first magnet and the second magnet, so as to align the power signal transmission module and the receiver module, and wherein the first magnet is configured to apply a magnetic field to the Hall sensor when in a second position relative to the user, so as to control the switch. a first magnet, the magnet for applying a magnetic field to the Hall sensor so as to control the switch; a power signal transmission module for transmitting an electrical power signal across the skin of a user; wherein the implantable portion (202, 301) further includes both a second magnet and a receiver module, the receiver module for receiving the power signal across the skin of the user, wherein when the first magnet is placed in a first position, the external portion is held in place on the user based substantially on the magnetic forces between the first magnet and the second magnet, so as to align the power signal transmission module and the receiver module, and wherein the first magnet is configured to apply a magnetic field to the Hall sensor when in a second position relative to the user, so as to control the switch.