Here's an idea I tried and it really worked well.
I simply tied a metal wind chime to the outside of my Grandmother's door when she was living with us. She had a habit of getting up in the middle of the night and wandering all over the house.
I was worried about her safety and I wanted to know when she left her room, but I wanted to be able to sleep through the night too.
So I tied a metal wind chime of bells to the outside of her door. I left my door open during the night and whenever I heard the bells chime, I knew she was up and out of her room.
It didn't look bad and was inexpensive, I picked them up at a garage sale. And they didn't seem to bother Grandmother either. Actually, I don't think she could even hear them at night with her hearing aids out!
This idea worked so well for us that we used it in later years when we had our own grandchildren visiting. It's just nice to know when a door is being opened, especially when you are responsible for someone elses safety.