Harleys and handsignals reminded me of something, and then Dwight gave me the answer

http://www.youtube.com/watch?v=qAygHtnyUqI

Going back to the original post, I've been on bikes, back and front for over 30 years, and I've never heard of the passenger giving the handsignals, nor have I ever seen it done.

Might even be disallowed under the highway code

Too old to die young, too ugly to leave a good looking corpse