title: How can I design an "invite friends" feature when my app is Android only?
body: <p>This  might be a stupid question but I can't find the answer. </p>
  
  <p>Snapchat and Instagram started as iOS only. How did they let you invite friends? Did they use the address book? What if I had an Android? Would I get a "Join me on Snapchat" invite, only to click a link and see "nah, you can't join"?</p>
  
  <p>Background:
  A friend and I have been working on an <a href="https://play.google.com/store/apps/details?id=ninja.sesame.app" rel="nofollow">Android productivity app</a>. </p>
  
  <p>We've got an idea for a social feature, it'd be a classic network effect. Users need to be able to invite friends from their address book. But we're Android only and don't have time to build a web or iOS app.</p>