A medical device includes a first housing portion (FHP) and a second housing portion (SHP) configured to be to be movable relative to each other from a first position to operatively engage at a second position to couple at least one of a drive device and a needle-inserting device supported by one of the FHP and the SHP to a reservoir supported by the other of the FHP and the SHP. Electronic circuitry configured to detect at least one of a first magnetic interaction between a magnet and at least one of a first magnetically attractive material and a first magnet-responsive device and a second magnetic interaction between the magnet and at least one of a second magnetically attractive material and a second magnet-responsive device, and to provide a signal or a change in state in response to detecting at least one of the interactions.