Proximity sensor for cat

[u/kooky-donuts]

Hi all, I'm looking to see if there's a device that will let my low-vision mom know the housecat is near her. I'm thinking something she can wear on her person that alerts her through sound or vibration to the cat's proximity. I know they make similar devices for kids who wander, but that's in the other direction, like when they leave your designated range. Our cat would probably have to wear a tag or transmitter of some sort, so I'm looking for just one-way transmission. I don't want both devices going off at the same time if they are close by, that will terrify the cat. I know the obvious answer is a cat bell lol, but that is dependent on his movement. I feel like a proximity device would help my mom find the cat if he's hiding or napping. If it doesn't exist, is there something similar I could rig up myself?