The same Privacy Policy can be used for both your website and mobile app, if it is adapted to include both platforms your business operates on.

If you already have this agreement for your website and you are now launching a mobile app, you need to first consider what kind of personal data you collect via the mobile app.

Then, update your agreement to include the new changes: what you collect from the website and the mobile app. Afterwards, notify users of these changes.

This agreement should be added regardless of the type of platform your business operates on or what kind of industry you are in:

Web sites
WordPress blogs, or any other platforms: Joomla!, Drupal etc.
E-commerce shops
Mobile apps: iOS, Android or Windows phone
Facebook apps (related read: Facebook: Privacy Policy for Login Dialog and App Details)
Desktop apps
SaaS apps (related read: Terms of Use & Privacy Policy For SaaS Applications)