From OzRunways FAQ.
When you pay for a basic OzRunways account it includes 1 tablet (e.g. iPad or Nexus9) & 1 phone (e.g. iPhone, Nexus6) to start with. You can add a second tablet personal backup for only $20 by adding that as a product on your account page, here:
https://www.ozrunways.com/store/account.jsp