Hi @AnnaMaria, a couple of ideas - there are small portable, battery-operated alarms that you could tuck into the glove box, the sensor would go on the door. The problem with them is that they are loud and may cause more problems than they solve. There is an alternative, though - it is a sensor that would go on the door, but rather than sounding an alarm, it pages the caregiver, and gives just a softer chime kind of sound.
There are also personal GPS devices that you can pin on his clothing in a place where he cannot see or access it. These come with an app, so that you can clearly see his location.
I hope that's helpful! - Warmly, Donna (team member)