Access parent app's helper methods from rails engine

All,

Is there a way to access a parent application's helper methods from a
Rails 3.1 engine?

I'm trying to create an engine which will call something like
"current_user" on the parent application to determine if a user is
signed in or not. I would like the engine to function regardless of
whatever authentication process the parent application is using. i.e.
simply relying on warden['env'] is not good enough.

Any help is truly appreciated.

Thanks!
Adam