aha so it appears that the platform implementations of this reference the winmd component, NOT the portable core dll.
I attempted to remove the winmd of GoogleAnalytics.Core and replace it with the same one referenced in the PCL, and although I can build when I do, at runtime i now get this error:
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.TypeLoadException: Could not find Windows Runtime type 'GoogleAnalytics.Core.Tracker'.
ultimately my goal is to define the tracker in my portable project (because that is where my viewmodels are defined) and call them at runtime with an instance of the platform tracker (loaded via MVVM Light's simpleioc)
so am I trying to do something that's not supported? if not what might I be doing wrong?