I have been using remote cameras in my sports photos a little lately an I often find I'd like to trigger one camera with another. In other words, remote camera way over there, another camera in my hand. I press and motor drive one camera, the remote camera starts and stops at the same time, with the first photo being close to simultaneous.
I have a pair of the Yougnuo triggers and these can be used to
1. Trigger a remote camera using one as a remote (press the button on Yougnuo)
2. Trigger a remote flash with the Yougnuo attached to the flash shoe of the camera in my hand.
But, you cannot as far as I can tell, trigger the remote camera with the camera in your hand.
Edit: My triggers are RF-603c's