Anyone have information about locator devices for people with dementia?

My father-in-law is looking for something that his wife with dementia symptoms can wear that will help him locate her around the house. They live on large property and although my MIL does not wander my FIL wants to be proactive so he can feel she is safe but doesn't have to be on top of her all the time. I have heard of trackers that can be worn as pendants but not sure of logistics of how they work. we are not sure how receptive she would be to wear something so the idea of jewelry or something similar may be appealing. thanks for any thoughts.