Soon, all Americans everywhere may be able to get help from 911 just by sending a text message.

The service is currently available only in certain areas and on the major national wireless carriers. But under new rules approved by the Federal Communications Commission Friday by a 3-2 vote, all cellular service providers will be required to support texts to 911 universally by year's end.

"Our first responsibility is to provide for the safety of Americans," said FCC Chairman Tom Wheeler, "and this is a step to continue to fulfill that responsibility. And it is not a final step."

Some 400,000 Americans contact 911 on a daily basis, according to the FCC — and roughly 70 percent of those attempts come from cellphones. In places where it's too dangerous for a caller to speak, or where the caller simply can't talk, text messaging could save the day.

Texting-to-911 comes with some unique challenges, though. Unlike calls from a cellphone, where getting accurate location data is a difficult but surmountable problem, it's unclear how text messages will be expected to convey location information automatically without the user disclosing it by hand. Dispatchers may not know where to send help in response to a texted plea to 911 — at least, not to the same level of specificity that a call from a landline can provide.

Republican FCC commissioner Ajit Pai said the FCC's vote encouraged people to "dive in… when in fact there's hardly any water in the pool," saying that even if wireless carriers complied with all the regulations on time, a tiny share of 911 dispatchers — around 2 percent — currently accept text messages.

The FCC's regulations will also apply to third-party messaging apps, like Google Voice and Apple's iMessage, that are increasingly popular among cellphone users. The proposal is controversial because although many Americans are switching away from texting to these "over-the-top" messaging services — leading consumers to think they can use them to contact 911 — requiring the apps to support the feature may be a complicated process.

There's the question of how the FCC will determine which third-party messaging apps will be covered by the rules. Technically, only apps that "interconnect" with text-messaging systems — meaning that they're set up to send messages to phone numbers as opposed to simply routing messages across the app's own systems — will be subject to the rules. Others, such as Republican FCC commissioner Michael O'Rielly, said putting 911 location requirements on software developers would lead to consumers' privacy settings being overridden.

Some worry that an eventual shift away from text-messaging technology altogether could undermine the regulation.

"Even the applications that have integrated with SMS, like iMessage, only fit the definition so long as the SMS technology remains in service," wrote AT&T in a blog post Thursday. "Once that technology is retired, those apps no longer fit the definition."

AT&T itself anticipates a shift away from traditional text messaging as telecom companies increasingly adopt Internet-based systems, and added that the FCC's rules might prevent the carrier from someday dropping support for the technology in favor of Internet-based messaging. Wireless carriers and some public safety officials have advocated for focusing on longer-term solutions such as a program known as next-generation 911, which is expected to support video and data coming from emergency callers.

But that's a long way off. For people who need to be able to reach 911 nonverbally in the short term, text-to-911 may be just the ticket.

"I guess we could sit here and wait until everything is worked out," said Wheeler of the push for next-generation 911. "But if one life is one too many… what are we going to explain to that life or his or her relatives? That we figured we'd sit and wait until the best of all possible worlds was possible? We're not doing that."