Board Game Arena

Lets say your friend is been away from the computer a while. Is it possible to manually send them a reminder email it is their turn during a game?

No, I don't think there's any way to do that. The closest thing I can think would be to invite them to a new turn-based game and click the "send an email invite" option. You could then delete the game and assume that when the friend sees the email and logs on they'll see it is their move. Of course, that's not really the intended use of that email functionality, but the it's the only option we have, I guess.