Medical alert systems that actually work in Miami?

My dad lives in Miami and he’s getting up there in age. Still very independent but it’s getting to the point where I think he needs a backup plan in case something happens. I found Bay Alarm Medical Alert while doing research but I have no clue how well it works here in Miami. He lives near Little Havana and spends time walking around the neighborhood. Anyone tried this brand here or another one that’s reliable? Need it to work no matter where he is.