It's a cell phone modem that only connects your house network using your local number.  The Verizon option is only a flat $20 per month and includes all long distance.  You still have caller ID and some other features, including 911.  Internet isn't used, just a good cell signal.  I put ours upstairs and connected it to an existing jack near an electrical outlet.  Just plug it in the outlet and connect it to the jack and you are off to the races!

It doesn't have anything to do with your existing cell phones, it just adds another cell phone line for the home network.