This afternoon Apple released an update to its “Find My iPhone” service which brought an iOS 7-optimized flat icon, as well as various bug fixes. However, it seems as if Apple pushed the update by accident, as the build number matches that available to Apple developers. But why shouldn’t you update? You can’t use the latest version unless you have a developer account.
Apple should be working to resolve the problem, likely with another update to the app that removes the developer account requirement. We’ll keep this post updated as more information comes up.