"The service is live right now in select cities and states right now. You can see the full list of where it applies here. If it isn't available in your area, worry not—the FCC has laid out a timeline that requires text-to-911 to be rolled out everywhere by the end of 2014. You'll also have the ability to send photos with your text, although that capability isn't supported everywhere yet either."
I like it from an actual-emergency standpoint, but you KNOW that asshats everywhere are going to be sending fake drunk texts to 911 with the wrong address. I foresee a massive wasting of time on the part of EMS.