Information about downloading IBM Cognos Mobile 10.2.1 FP4 is available on the Downloading IBM Cognos Mobile 10.2.1 FP4 page.
Cognos Mobile 10.2.1 FP4 contains both product corrections and new features in the server and the native apps. For Apple iPhone and iPad the IBM Cognos Mobile native app and the IBM Cognos Mobile for Good Technology native app are available from the Apple Store. For Android the IBM Cognos Mobile native app is available from Google Play.
The fix list for this fix pack can be found here.