Get Gift item with a product.

Hi,
I want to add functionality to get a gift item with product. i.e. There will be a category of gifts, user purchase a  product and then he is asked to chose any gift from "Gifts" category and checkout the order with this gift item. He is not allowed to get gift alone. Gift price should be some proportions with order total. Actually it is a simple idea but I want to extend more. Is it possible and how? Thanks,

Atiq.

This may give you ideas, but "choosing" from a category may be more difficult.