A detector for detecting the removal and/or insertion of a firearm out of and/or into a holster. The detector may transmit a message each time the firearm is removed from the holster. A recording system may receive the message and determine whether or not it will begin recording the data it captures. A detector may detect the change in a magnitude of an inductance and/or an impedance of a circuit to detect insertion and removal of the firearm into and out of the holster. The holster is configured to couple to the detector to position the detector to detect insertion and removal of the firearm. An adhesive tape may couple a detector to a holster.