Today marks the launch of Text-to-911, the technology that allows people use their phones to text police about an emergency. The 911 texting feature is fairly straightforward: text your emergency and immediate location to 911, and police or fire will be dispatched by the same operators. Adding the location is necessary, because texts can't be traced the way a phone call can. 

The rollout is still in its early stages, and dialing 9-1-1 is certainly a much smarter move in emergencies. The text ability is not available in all locations yet (as of now, the technology exists in these specific counties [PDF]) but it does work on each of the four major mobile carriers: AT&T, Sprint, Verizon, and T-Mobile. It's attempting to be an alternative for summoning help at times when making a call is not option. But when are those times?

The feature can be used by deaf or hard-of-hearing people who might not have another way to call for help. The 911 service does have the capability to answer TTY (TeleTypewriter) calls, a computer-phone device that allows the hard-of-hearing to communicate over landlines. The FCC still recommends first using TTY and telecommunications relay service before trying to text 911. But those options aren't always available on the go, while someone's cellphone could easily be in reach.

The other situation in which text to 911 would be helpful is, in the FCC's words, "if a voice call to 911 might otherwise be dangerous or impossible." That might be a situation in which making noise would increase the danger, like if you're hiding from an intruder or are being chased. It could also come into play if you're an area where cell service is spotty and calls are difficult to connect. 

Or it could include a time when a person is unable to speak, like say if they were choking. Or, if your nightmares run more toward horror movies, if the person is gagged or tied up, but can still reach a phone with their fingers. You might even want to practice texting without looking at your phone, like Matt Damon's rat fink character in The Departed.

These are grim scenarios, of course, but it's always better to be prepared.