Hi Cindy ~
This is an AWESOME question that you posted, and I'm sure many others have the same concerns & questions.
As a former 911 Operator for the City of Los Angeles, I can tell you that NO MATTER WHAT you here on the radio shows or see on the news - NOTHING is as reliable as a land line in the event of an emergency. Yes, it's true that we have the ability to "track" a cell phone call, but it's only within 500 ft or so, and if you are incapacitated in any way & cannot tell the operator EXACTLY where you are (in a car, inside a home, at the bottom of a ditch, etc...) help MAY arrive too late, and every second counts.
The same is true for VOIP callers. I took a call one time from a man regarding his deathly ill mother...he told me all her symptoms, what was happening to her, etc...I verified with him the address that was coming up on my screen & sent help. When the Police & Paramedics got there, there was no such person at the location with a problem of any kind. I called the man back & discovered that, in his atress & anxiety, he verified his OLD ADDRESS that the VOIP was registered to. In fact, he was in ANOTHER STATE! He had forgotten to notify his service provider of his change of address when he moved...(with ALL the other things on your mind when you move - notifications you have to make - this is a very common area that is overlooked)
I hope I have shed some light on this aspect of your question & I ALSO hope that whomever else reads it will REALLY heed this "safety warning". If you don't use your landline for anything else, the bill will not be that much. AND, wouldn't you rather pay just a small bill to have the piece of mind?
Good luck to you, mama!