Slide to Play writes:
"The arcade classic Silent Scope was known for its unique hardware--the replica sniper rifle controller pointed at the arcade screen contained a smaller screen inside the scope, allowing you to gauge distances near and far while you carefully aimed your shots. The iPhone is an impressive piece of hardware as well, but with only one screen, some changes had to be made to fit the new platform. We sighted down Konami's iPhone port of the game at a press event last Thursday, and came away feeling that its aim is true--for the most part.
Since you no longer have a second screen to peer into, all of the action takes place on the iPhone's touch screen, which becomes a sniper's reticule when you double-tap to zoom in on a target. You can still fire from a distance, but the pixel-high bad guys are almost impossible to hit without zooming in."