Iphone application / customization

I need an iphone application or some iphone setting that will make my iphone only use half the screen, so all the graphics will be displayed concentrated on half the screen, the other half will be just black, also i need a screensaver or other feature that makes the whole screen shut down or be black on my command. This project is for my private use so it doesnt need to be applestore friendly or anything like that.