You can buy safety pendants that contain a GPS tracker hooked up to the cell network. It has an emergency button and can be located through the service's website. Some even have a speaker and mic so you can talk to an agent through it. I'm sure they could add a feature where if the pendant is a certain distance from home then have an alert go out to a list of contacts. Buy two of them for grandma if you really want to make sure that she is never not wearing one.