I like to work restrained recalls with puppies. Have person A hold the collar while the owner walks away, calling, skipping, and getting the pup's attention and excitement up.
Have pieces of something REALLY good (hotdog, cheese, left-over meat). On your cue, call the pup and have the person release their hold on the collar. Pup comes flying to you!
There's also a video out called The Really Reliable Recall which is being lauded on the Agility lists. I haven't seen it yet.