I was recently on the phone with a Verizon wireless customer service representative. He told me that even when my cell phone reads “No Service”, which is actually quite common where I live, that 911 will still work. I don’t see how this could be but he assured me that it was a new feature that they were instructed to tell every customer that called in. I don’t really want to test it to find out for sure.
Possibly more useful is the service “Free 411”. Simply call the toll free number (1/800-FREE411), listen to a short ad lasting ten seconds or so, and get the desired phone number for free.