My old lady i'm old myself is out of balance continously and she fells many times, when i'm around i'm able to help her, sometimes i'm in another room and she has to shout and that break my heart. i bet u have seen those tv ads about a lady falling, but she, fortunetely, has a device around her neck that can get help by calling a place. Now, i'm not asking u for a medical advice but if my old lady had something around her neck to call "me" derectly .instead of that place. i really appreciate some help. i used to be a lab tech.

 

http://www.info4cellphones.com/cell-phones-for-children.html

use a cell phone with large programmable speed dial buttons.

Childrens phones that only dial you no matter which button is pushed. It could be put on a necklace.

Much more versatile than anything you could build yourself. And other people can be reached if you are not available, being another option

 

How about a "can-of-air" horn? BEEEEEP!
Or a pushbutton, battery and loud buzzer? BUZZZZZ!