Detect app is running on Kindle Fire

You can read android.os.Build.MANUFACTURER and android.os.Build.MODEL. On a Kindle Fire 1st Generation they are 'Amazon' and 'Kindle Fire' respectively. For model codes of newer Kindle Fire devices, see Device and Feature Specifications on Amazon's developer site.

Based on Amazon's Tablet Device Specifications I currently use this code:

public static boolean isKindleFire() {
    return android.os.Build.MANUFACTURER.equals("Amazon")
            && (android.os.Build.MODEL.equals("Kindle Fire")
                || android.os.Build.MODEL.startsWith("KF"));
}

According to that table the manufacturer string is always equal to "Amazon" and the model string is either "Kindle Fire" for the first 2011 model or it starts with "KF" for all subsequent models.