I used this sensor and simply wired it into a contact sensor (i.e. it replaces the magnetic reed switch.)
https://www.amazon.com/Universal-Automobile-Occupancy-Detection-Accessory/dp/B0BTBYDP9Q
I used this sensor and simply wired it into a contact sensor (i.e. it replaces the magnetic reed switch.)
https://www.amazon.com/Universal-Automobile-Occupancy-Detection-Accessory/dp/B0BTBYDP9Q