Anybody have experience with infrared bed alarms?

My 86 year old mother lives in my home. She has dementia and a myriad of other health issues. She can hardly walk but can get herself up during the night to use her bedside commode. She is at risk of falling. I am wondering if an infrared alarm can be set up in a way that allows her to get herself up to toilet but would go off if she strayed too far away. We already have a wireless doorbell taped next to her bed and baby monitors. I would like to be able to sleep through the night myself without worrying that she has fallen.