Sensor for pocket door

Does anyone have any suggestions for instillation of a sensor on a pocket door? The door opens in, so the sensor would have to be installed on the outside for it to work (which defeats the purpose of having an alarm sensor). I previously had AT&T digital life, and they had installed a recessed sensor in the door. I doubt it would be compatible with Ring. Do you know of any recessed sensors on the market that are compatible with Ring?