How to create a full phone image from a Screen Capture?

have an app that I'm trying to market and want to use a full image of the iPhone with screen shots from my app

The image would look similar to this
http://draykenobi.files.wordpress.com/2009/08/iphone-app-store1.jpg

The difference is that my screen capture would be shown on the iPhone. I know how to do the screen capture, but I really like the look with the phone around it.

I have photoshop, but can't seem to find any templates where I could just add my screen shot into the psd.

Does anyone know of how I can achieve this easily. Maybe there's an app that does this?

Thanks