Apparently OpenFeint supports both iOS and Android. Great.
But how do I integrate it with cocos2d-x Android? The SDK is, apparently a .jar and such. Cocos2d-x uses c++.
I don't get this tutorial: http://blog.molioapp.com/2011/11/openfeint-and-admob-integrated-with.html
I copy & paste the code and immediately I get errors (JavaVM *gJavaVM;? There is no identifier called that way!)
Are there any other steps not mentioned in that tutorial I missed?
Yes. In order to build a C++ library for Android you need to use the NDK. Getting that set up is pretty involved so I am just going to link you to a separate tutorial that has already covered it.
http://developer.android.com/sdk/ndk/index.html#installing
That is the Google documentation on getting up and running. There are other resources for this as well if you have trouble.