A retainer apparatus including a first retainer portion, a second retainer portion, a transceiver, and a sensor comprising a motion detector. The retainer apparatus includes the first retainer portion configured to be slidably attached to a first harness strap and a second retainer portion configured to be slidably attached to a second harness strap. The first retainer portion is removably attached to the second retainer portion. The motion detector is configured to detect movement of the retainer apparatus and transmit a warning signal, via the transceiver, to a controller within a vehicle comprising the retainer apparatus to alert a user in the vehicle if the movement is detected.