Resizing a window to a specific size, for screen recording?

Question

I want to record an application window for a demo/tutorial, and I'd like the video to be a particular resolution.

Is there a trick/tool already installed in Lion that allows me to take a window and resize it to a specific resolution? For instance, take a window and resize it to 1280x720 in preparation for a HD 720p video recording?

If not, is there a tool I can get from the internet that will do this for me?

It just occured to me that perhaps Automator would help me here, but I'm not able to find an action to resize a window. An Automator script is OK as well.

Basically, any free/cheap tool/trick/script that would do this.