Apple has banned the practice of giving out in-app rewards for installing another app. You can still give a reward for a user clicking a link which redirects them to a page on the App Store - but you cannot condition your reward on the user actually installing the app, only on their choosing to view the page where, if they want, they can CHOOSE to install the app.
To do this, you just open a MobileSafari session to a web page which tracks the page load (for your analytics) and redirects to an App Store URL for the app you're promoting. The easiest way to do this is to use a URL shortener that provides analytics on users of the short link.
