Reverse 911 means that if you call 911 from the landline, they can trace the call back and see on their screen your address even if you are unable to speak. If you are too hurt to speak, do not know the address etc etc they can still see immediately where you are to send help. Cell phones can only be traced to the closest tower which gives them an area, not an address.
Just to clarify....911 service (in most areas) will automatically do the above when you are
calling from a land line. So, if you call 911 and can't speak, panic and can't remember your address, a young child calls, etc, the 911 dispatcher will still know where to send an ambulance, police car, etc.
On the other hand, not all communities have Reverse 911 at this time. Here's the Wikipedia definition of Reverse 911: Reverse 911 is a communication system that allows emergency services to quickly contact members of a community or organization with information. It is so named, because 911 is the telephone number used for members of the community to communicate with emergency services (police, fire, EMS) in the USA. This system allows emergency services to do the "reverse", usually to inform the public of a known hazard. Reverse 911 is designed to provide map or list-based communications with key audiences. Geographic calling zones are created based on immediate circumstances (e.g. Amber Alerts) or ahead of time based on anticipated needs (e.g. flood plains). Reverse 911 may also target specific lists of people (e.g., first responders, Neighborhood Watch, etc.) Reverse 911 is used in hundreds of communities, counties, commercial businesses, schools and non-profit organizations. The system has been used to solve and prevent crimes.[1]
Disclosure
: I work for Verizon (Landline) in the department that does 911 addressing for my state. This info is used for both inter-company purposes, and we also contract out the info/work to most counties and cities. Everyday I see the amount of work that goes into providing this info to make sure you and your family receive accurate 911 addressing. In short...we save lives, because without our service the emergency vehicles have much less of a chance of making it to your home correctly. If you're using a cell phone to call 911, that protection disappears. Most cell phones do have GPS capability, but it's only accurate to a few hundred yards...which means the emergency vehicle will probably end up at the wrong house.
In the end, it's a personal decision...is insuring the safety of your family worth approximately $20 a month to you?