For one of the approaches, please see these CodeProject articles:
WCF and Android Part I[
^],
WCF and Android: Part II[
^].
As far as I can see, this article is limited to the case when you only consume the service in Android, and not developing an Android service, but second option looks quite unlikely.
Generally, if you had CLI-based WCF on both sides, you would have all the WPF options at your fingertips, but unfortunately Xamarine makes it quite expensive, so the suggested approach looks like a good choice.
—SA