Verizon has ... I forget the name for it, it's a cell phone in a box.  Kind of a square hockey puck.  You can have your house phone number transferred to it.  Disconnect your house phones at the demark (the box on the house), plug into your house phone network anywhere convenient, and you have dial tone and it works just like the house phones.  I think the only change is not dialing 1+ for long distance.  We have 4 of them

Frontier has been unable to provide reliable service to my Mom's house. transferred her number, plugged it in and put on a shelf in the living room behind a clock, and instead of noisy lines or no service she has clear reliable phone service.  And there's no additional charges for long distance.

Our home phone was getting a huge number of telemarketing calls.  Plus our landline cost was too high for what we use it.  Because I have a business account I can add another cell line for $20.  That's about $50 a month less than Frontier.  Because of the telemarketing calls we changed numbers when we did it.  Since this is a cell phone (theoretically) telemarketers aren't supposed to call.

To meet state requirements the church elevator has to have a dedicated phone line that when you pick up the phone it dials a 24 hour response center.  Rather than spend $70-100 a month for a line never used (it HAS to be only for the elevator) I got a home box and an auto dialer.  Pick up the phone in the elevator and it dials the local fire dept (I was Chief at the time).  If no answer it forwards it to 911.

Mother in law lives alone and has had occasional landline problems.  We got her a box and put it on a separate phone in her bedroom.  She likes the fact long distance doesn't cost any extra.

This is one of those places technology amazes me.  Early 90's I worked for an office supply house that sold cell phones.  A customer needed a second independent line for security purposes  We got a system to do that. It was a box about half the size of a coffin and cost $2-3000.  Now we do it with a hockey puck for almost nothing.

OK typos fixed... I hope