Since yelling for help isn't an option, you might want to look into a "professionally monitored medical alert system" that connects to a monitoring centre, which can dispatch local emergency services for you.
Just make sure you look for features like fall detection and GPS tracking.

One thing that comes to mind is a wall-mounted button. You can place these in every room, and they have a large button that you can easily press for help. Some companies offer a base station with a powerful speaker and microphone that acts as the main hub. You get multiple wall buttons, and they are a one-time purchase and not very expensive. There is a monthly service fee, though.

If you can't pay the monthly fee, there are some unmonitored systems that you can put a few phone numbers in, like a relative's number or 911. When the button is pressed, it automatically calls or texts those numbers. The downside is, if those contacts don't answer, there is no backup plan.

One more thing to think about is vibrating alerts or visual cues, such as flashlight lights.
Hope I helped, but you need to do some research to find what suits your situation the best. I just gave you some ideas on where to start.