Flip the source clip to one direction to reveal the incoming clip, or flip the destination clip over the entire frame.

http://fxfactory.com/misc/FxFactoryHelp/pluginguide/transitions/pageflip/index.html

FxFactory is a revolutionary visual effects architecture powering hundreds of plug-ins for Final Cut Pro, Motion, Final Cut Express and Adobe After Effects:
http://fxfactory.com/fxfactory/

Genie Filter & Transition for Final Cut Pro, Motion and After Effects

Hot tutorials of motion graphics and visual effects in Final Cut Pro, Motion and After Effects using FxFactory from Noise Industries.