Imagine having an emergency in your home and needing to find something that will solve the problem. You need to be able to put your hands on it quickly.
A fire extinguisher hung in a conspicuous place, easy to reach, is a prudent precaution. Everyone in the house should know where it is and how to use it if it is necessary.
A water meter key could easily divert another kind of household disaster assuming it could quickly and easily be found and if a person knew how to use it to shut off the water to the home.
With household water pressure generally below 100 pounds per square inch, a significant amount of water can still be dispersed into a home if a pipe were to burst. That amount of water can do drywall and floor damage, as well as cause losses to electrical appliances like TV's, clothes, furniture and other things.
While some houses may have a main shutoff valve separate from the meter, the question would be if all of the occupants knew where it was and how to operate it.
Purchase a water meter key from a local hardware or box store and learn how to use it. Once the meter is open, a wrench is needed to close and open the valve. Some water meter keys have a wrench on the other end of the key making a separate wrench unnecessary.
Consider hanging the water meter key next to the fire extinguisher so that both are easily found. Training the responsible parties in the house is also necessary to minimize damage.