title: How Did GroupMe verify my number?
body: <p>I am working on an iPhone application where I need the user's phone number. From what I've read (here for instance - <a href="https://stackoverflow.com/questions/193182/programmatically-get-own-phone-number-in-iphone-os">Programmatically get own phone number in iOS</a>), the device's phone number is not available within your application's container. I've always had the user enter his or her own number. But when I joined GroupMe the other day, after clicking the Get Started button, my phone opened up a drafted text message to some US area code number "Send this text to verify your phone number(b2bd308eb7)" After I sent the text, the app knew my number....how does one implement a system like this? </p>