Since OS X 10.2 Apple has included a Chess game by default on your Mac. The current version allows you to play against the computer with varying difficultly levels, play against another person, and even play online. You can change the look of the 3D board, hear moves and even speak to make a move. You can also save and resume games.
Gary,
Is there an iPhone equavalent of iMac's chess?
Ray: There is no Apple-produced app, no. But a quick search of the iOS App Store comes up with dozens of Chess apps.
Nice one Gary I have no idea it was there thank you