That you could leave on the bedside table next to your gun, and it's programed where you can hit a button and it pings your cellphone wherever you may have left it in the house, and dials 911?

You could have hands-free comms with 911, or even have an option for a pre-recorded message to the 911 operator, (Address,name, physical descriptions of dwelling occupants, etc.) in case you had to move to a different room.

You could easily do it with a simple land line and a speakerphone with speed dialer...

What is this "land line" you mentioned?  I'm not familiar.