The newest Find My iPhone app (v1.1) has just been released and includes improved support for iOS 4 devices. If you are running an older version, it's important to update as previous versions are no longer supported.
To update to the newest version of Find My iPhone, visit the
App Store on your device and select Updates. Signing in to an earlier version of the Find My iPhone app will also take you directly to the App Store where you can update for free.
via apple.com
