invite a Android Friend

Hello,
i have a couple of friends that only play on android, they dont want/need/have link to facebook.
Is there a way to invite them as friends without the facebook login?
Is there a search or a invite by ID?

Thanks in advanced.

I'd like this addition if it isn't already possible as well!

me as well, I have non-facebook friends playing on android and iphone but am unable to add them to my friends list.
A search field should be available for finding users and/or clubs.