A seatbelt ignition interlock system. The system includes a plurality of sensor devices each including a housing, a latch configured to removably engage the latch receiver of a vehicle seatbelt system, a latch receiver configured to receive and removably engage the latch of the vehicle seatbelt system, a latch sensor, a temperature sensor, and a power source. Each sensor device is in electrical communication with a vehicle ignition interlock circuit, and the vehicle ignition interlock circuit is in electrical communication with an ignition of a vehicle. The vehicle ignition interlock circuit is configured to prevent the vehicle ignition from being started when a combination of temperature sensors and latch sensors determine that occupied seats have unfastened seatbelts.