Widgets in the header area

Hi, I’m not sure if my question is dependent on the theme (if it is let me know).

I notice a lot of WP themes have big image areas that cover the top of the home page. Example: http://kaptinlin.com/themes/striking/

How simple/difficult is it to fit or overlay a widget in that area? I’d like to put something like a short form submission or a custom search box over that area.

Thanks