With Americans sending nearly six billion texts every day and over 2.2 trillion annually, it seems only natural that when an emergency strikes, many people would want to grab the nearest cell phone and text 911 for help.

That option moved closer to reality this week, when four major wireless carriers rolled out a text-to-911 feature. AT&T, Verizon, Sprint and T-Mobile met the Thursday deadline to enable text-to-911 service, giving people a way of reaching emergency responders when a voice call is not an option.

But so far only a limited number of municipalities in 16 states are able to respond to emergency texts.

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Local emergency call centers (known as public safety answering points, or PSAPs) are responsible for implementing this service in their counties, and many have not yet done so.

"The unfortunate truth is that, on the whole, PSAPs are not where they should be and need to be on text-to-911," FCC Chairman Tom Wheeler said in a statement. "It's been more than a year since the FCC secured a commitment from wireless carriers serving 90 percent of Americans to deploy text-to-911 by 2014. Yet today, only a small fraction of PSAPs are ready to support text-to-911. We've done our part. Now, the PSAPs must do theirs."

The FCC expects the number of PSAPs accepting texts to grow over time and provide the service in more areas.

Still, text-to-911 may not be the best option in an emergency. The FCC warned that "even where text-to-911 is available, if you are able to make a voice call to 911, and if it is safe to do so, you should always make a voice call to 911 instead."

Experts warned that the time needed to compose a text and locate a caller, as well as lack of information or context in a text message, could interfere with helping those in emergency situations.

"If somebody is running from the scene, we need to know what that person looks like, because in a few minutes, you may not remember what they look like," Kimberly Murch, a dispatch supervisor from the California Highway Patrol, told CNET's Sumi Das in an interview.

Information gleaned by dispatchers over a phone call, such as background noise or the caller's emotional state, also cannot be determined from a text.

"You can tell if somebody is under a lot of stress, if they're experiencing an emotional situation -- this is usually not a good time for a caller; they've witnessed a crime," Murch added. "They've witnessed something happening to them, or they've experienced it. You can hear that in their voice, you can tell which direction you need to take the questions to."

However, there are some texting success stories. Kent Hellebust, a vice president at TCS -- a texting management software company -- said that a ten-year-old girl was able to successfully get help by texting 911. Apparently, composing a text felt more natural to her than dialing in, reported CNET.

If the caller is deaf, hard-of-hearing or has a speech disability, using a TTY or a telecommunications relay service is the recommended course of action. The FCC stresses that sending a text to 911 should only be used as a last resort.

The National Emergency Number Association (NENA) has suggested some possible options for PSAPs that do not currently have text-to-911 services, including text-to-TTY and a web portal for receiving text messages. However, 25 percent of the nation's emergency call centers still do not have high-speed Internet, according to NENA.

Looking towards the future, Trey Forgety, a NENA spokesperson, told CBS News in an email that next-generation 911 systems will be able to accept voice, text, images, video and data. But these technologies, Forgety says, "are not yet ready for prime time."

"The speed and geographic extent of deployments will depend on state and local funding for 9-1-1 systems, which has, in some cases, been diverted to other, non-9-1-1 related purposes," he added.

Forgety says that expanding the service will all come down to three things: technology, support and funding. Text-to-911 services must be supported by both the carriers and the local emergency call center -- all major cell phone providers are unlikely to support the same PSAP at the same time, he noted. In addition, translation and texting services would not likely be available immediately.

"While legacy support for text over TTY/TDD is already available at all 9-1-1 centers, many will choose to implement text using a secure, browser-based process or an interim IP-based process," he told CBS News. "Now that [text-to-911] requests can be submitted to carriers, it is likely to take 2-3 years before text support at local 9-1-1 centers becomes widespread. National coverage is likely to take even longer."